Method for the manufacture of cyclododecasulfur

ABSTRACT

The present invention relates to a method for the manufacture of cyclododecasulfur, a cyclic sulfur allotrope wherein the number of sulfur (S) atoms in the allotrope&#39;s homocyclic ring is 12. The method includes reacting a metallasulfur derivative with an oxidizing agent in a reaction zone to form a cyclododecasulfur-containing reaction mixture.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.15/440,056 filed on Feb. 23, 2017, which claims the benefit of U.S.Provisional Patent Application Ser. No. 62/302,213 filed on Mar. 2,2016, the disclosures of which are incorporated herein by reference intheir entirety.

PARTIES TO JOINT RESEARCH AGREEMENT

Inventions disclosed or claimed herein were made pursuant to a JointResearch Agreement between Eastman Chemical Company and the UniversityCourt of the University of St. Andrews, a charitable body registered inScotland.

FIELD OF THE INVENTION

The present invention relates generally to a method for the manufactureof a cyclic sulfur allotrope, and specifically cyclododecasulfur,wherein the number of sulfur (S) atoms in the allotrope's homocyclicring is 12.

BACKGROUND OF THE INVENTION

Cyclic sulfur allotropes and routes for their synthesis fromsulfur-containing moieties have been described in the literature. Forexample, cyclododecasulfur, also referred to herein as S₁₂, is known tobe present in thermally equilibrated sulfur allotrope mixtures inconcentrations dependent on the equilibration temperature, ranging fromabout 0.39 wt % to 0.49 wt % between 116° C. and 387° C. (see Steudel,R.; Strauss, R.; Koch, L., “Quantitative HPLC Analysis andThermodynamics of Sulfur Melts”, Angew. Chem. Int. Ed. Engl., 24(1),1985, pp. 59-60).

Steudel et al describe a method for S₁₂ synthesis in whichcyclooctasulfur, also known as S₈, is heated to an equilibrationtemperature of 200° C., cooled to 140° C., and quenched in liquidnitrogen. S₁₂ is recovered from the solid allotrope mixture by multipleextractions, recrystallizations, decantations, and filtrations from verycold carbon disulfide with an overall yield on the sulfur fed ofslightly over 0.21 percent. The melting point of the purified S₁₂ isreported as 146-148° C., the generally quoted melting point of purifiedS₁₂. (Steudel, R.; Mäusle, H-J., “Detection of Large-Ring SulfurMolecules in Liquid Sulfur: Simple Preparation of S₁₂, α-S₁₈, S₂₀ fromS₈”, Angew. Chem. Int. Ed. Engl., 18(2), 1979, pp. 152-53; and, Steudel,R.; Eckert, B., “Solid Sulfur Allotropes”, Topics in Current Chemistry(2003) 230, pp. 1-79).

Schmidt and Block describe a method for the synthesis of S₁₂ in whichsulfur is heated at 200° C. for 10 min and quenched in water. Theresulting solids are stirred for 12 hours with a 6:1 mass ratio of CS₂at room temperature, followed by filtration of insoluble polymericsulfur, concentration of mother liquor, and recrystallization of crudeS₁₂ from the remaining liquor at −30° C. The remaining S₈ is dissolvedout of the S₁₂ solids with CS₂, and S₁₂ crystals are dried. The driedS₁₂, at a yield of 0.1% of the feed S₈, has a melting point of 140-142°C., with a higher melting point of 146-148° C. after recrystallizationfrom benzene. (Schmidt, M.; Block, H.-D., “Occurrence ofCyclododecasulfur Compound in Sulfur Melts”, Angew. Chem. Int. Ed.Engl., 6(11), 1967, pp. 955-56).

Mäusle and Steudel describe a cyclic sulfur allotrope synthesis methodin which dichlorodisulfide dissolved in CS₂ reacts with aqueoussolutions of potassium iodide to form unstable diiododisulfide andpotassium chloride, which spontaneously decomposes into a mixture ofeven number homocyclic rings S₆, S₈, S₁₀, S₁₂, S₁₈, and larger, and 12.Typical yields are 36% S₆ and about 1 to 2% 812. (Mäusle, H. J.;Steudel, R., “Simple preparation of Cyclohexasulfur (S₆) fromdichlorodisulfane (S₂Cl₂) and ionic iodides”, Z. Anorg. Allg. Chem. 463,1980, pp. 27-31).

Yet another approach to the synthesis of S₁₂ is described by Schmidt andWilhelm (Schmidt, M.; Wilhelm, E., “Cyclodocecasulfur, S₁₂ ^(”), Angew.Chem. Int. Ed. Engl., 5(11), 1966, pp. 964-65). This method includes themetathesis of dichlorosulfides with polysulfanes, with correspondinggeneration of by-product HCl:Cl₂S_(x)+H₂S_(y)→2HCl+S₁₂ with x+y=12

Schmidt and Wilhelm combine dropwise mixtures of S₄Cl₂ in CS₂ and H₂S₈in CS₂ into a mixture of diethylether and CS₂ over 25 hours. Aftertwelve hours, crude Sit crystals are filtered off periodically. Theresultant crude S₁₂ is redissolved in CS₂ held at 40° C., andrecrystallized by concentration of the crude S₁₂—CS₂ solution. Finalrecrystallization is from benzene, with an overall S₁₂ yield of 15% to20% based on the sulfur fed.

Yet another method for cyclic sulfur allotrope synthesis involves thereaction of a sulfur transfer agent,bis(π-cyclopentadienyl)-titanium(IV) pentasulfide, (titanocenepentasulfide) or (C₅H₅)₂Ti(S₅) with sulfur dichloride (SCl₂) to formtitanocene dichloride, S₆, and some S₁₂. In this method, (C₅H₅)₂Ti(S₅)in CS₂ is treated with SCl₂ in CS₂ at 0° C. The filtrate containing S₆and S₁₂ is filtered from the titanocene dichloride precipitate andevaporated to give an orange-yellow precipitate. S₆ is dissolved withcold CS₂ and the remaining solids are dissolved in hot CS₂. S₁₂ isrecovered by cooling and crystallization from the final CS₂ solution.The overall sulfur yield is 87% to S₆ and 11% to S₁₂ (see Schmidt, M.;Block, B.; Block, H. D.; Köpf, H.; Wilhelm, E., “Cycloheptasulfur, S₇,and Cyclodecasulfur, S₁₀—Two New Sulfur Rings”, Angew. Chem. Int. Ed.Engl., 7(8), 1968, pp. 632-33).

Prior art methods for manufacturing cyclic sulfur allotropes all sufferfrom one or more drawbacks such as low yields, multiple convolutedmanufacturing steps, expensive, complex, and limited-availabilitystarting materials and intermediates and tedious isolation andpurification of end products. Most work in this field has accordinglybeen limited to academic endeavor, and commercially acceptable methodsfor cost-effective, efficient large-scale production have not heretoforebeen reported. A continuing need therefore exists for a robust,high-yield, safe, and cost-effective method for the manufacture ofcyclic sulfur allotropes, and specifically cyclododecasulfur, that meetsindustrial criteria for commercial implementation.

SUMMARY OF THE INVENTION

The present invention relates to a method for the manufacture of acyclic sulfur allotrope, and specifically cyclododecasulfur, wherein thenumber of sulfur (S) atoms in the allotrope's homocyclic ring is 12. Themethod includes reacting a metallasulfur derivative with an oxidizingagent in a reaction zone to form a cyclododecasulfur-containing reactionmixture that contains the cyclododecasulfur. The method preferablyfurther includes isolating the cyclododecasulfur from thecyclododecasulfur—containing reaction mixture. The method of the presentinvention is particularly useful for the manufacture ofcyclododecasulfur, described herein as a cyclic sulfur allotrope having12 sulfur atoms in the homocyclic ring, that is useful in vulcanizingcompositions for use in forming a vulcanized article, as disclosed andclaimed in pending U.S. patent application Ser. No. 15/015,165 havingcommon assignee herewith, the disclosure of which is incorporated hereinby reference.

Further aspects and areas of applicability will become apparent from thedescription provided herein. It should be understood that thedescription and specific examples are intended for purposes ofillustration only and are not intended to limit the spirit and scope ofthe present invention.

DETAILED DESCRIPTION

As utilized herein, the following terms or phrases are defined asfollows:

“Cyclic Sulfur Allotrope” means a sulfur compound characterized by ahomocyclic ring of sulfur atoms.

“Cyclododecasulfur” means a cyclic sulfur allotrope with twelve sulfuratoms in its homocyclic ring, also referred to herein as S₁₂.

“Metallasulfur derivative” means a compound containing divalent sulfur(S) atoms and metal (M) atoms with a ratio of sulfur to metal atoms ofat least 2:1 (S:M≥2.0). The defining structural unit of such derivativesmay be represented as:

In which the metal atom (M) may be divalent or multivalent and thesulfur atoms (S) are divalent and form a chain with n≥0. The compoundmay be linear or branched, it may be cyclic, multicyclic, oligomeric orpolymeric and it may contain other elements, ligands, cations or anionsbonded or coordinated to the metal atom (inner- or outer-sphere),without limitation.

“Metallacylcosulfane” means a metallasulfur derivative with at least onecyclic structural feature containing sulfur and metal atoms, preferablyonly sulfur and metal atoms, with at least two sulfur atoms and one ormore metal atoms.

“Sulfur templating agent” or “Sulfur templating agents” mean a compound,or combination of compounds and elements, which when reacted withelemental sulfur form a metallasulfur derivative.

“Oxidizing agent” means an agent which is (i) reduced by a metallasulfurderivative; (ii) promotes the release of the sulfur contained in themetallasulfur derivative and (iii) does not add sulfur from itscomposition to the cyclododecasulfur being produced in the process.

“Pseudohalogen” means a molecule or functional group with properties anda reactivity profile similar to a halogen (see e.g. Inorganic Chemistryby Duward Shriver, P. W. Atkins and Cooper Langford, W. H. Freeman &Co., 1990, pp 407-408).

The present invention is a method for manufacture of a cyclic sulfurallotrope, and specifically cyclododecasulfur, wherein the number ofsulfur (S) atoms in the allotrope's homocyclic ring is 12. Similarmethods may be used to form polymeric sulfur, and are claimed in acopending application filed herewith having common assignee.

The method of the present invention includes reacting a metallasulfurderivative with an oxidizing agent. A suitable metallasulfur derivativeis characterized by the formula

-   -   wherein    -   L is a monodentate or polydentate ligand species which may be        the same or different when x>1;    -   x is the total number of ligand species L and is from 0 to 6        inclusive;    -   M is a metal atom;    -   y is the total number of metal atoms and is from 1 to 4        inclusive;    -   S is a sulfur atom;    -   z is the number of sulfur atoms, and is from 1 to 12 inclusive;    -   u represents the charge of the metallasulfur derivative and may        be from −6 to +6 inclusive;    -   v is the number of metallasulfur derivative units in an        oligomeric or polymeric structure;    -   I is an ionic atom or group and may be cationic or anionic;    -   and w is the number of cationic or anionic atoms or groups, as        required to provide charge neutrality.

The ligand species may be mono- or polydentate and may be charged orneutral. Suitable ligand species are cyclopentadienyl or substitutedcyclopentadienyl rings; amines such as primary, secondary, and tertiaryalkyl or aryl linear or cyclic amines and may also be diamines ortriamines or other polyamines such as ethylenediamine andethylenetriamine and their derivatives, piperidine and derivatives, andpyrrolidine and derivatives; or heteroaromatic derivatives such aspyridine and pyridine derivatives or imidazole and imidazolederivatives. Preferred amines include but are not limited to tetraalkylethylenediamines, such as tetramethyl ethylenediamine (TMEDA),tetraethyl ethylenediamine, tetrapropyl ethylenediamine, tetrabutylethylenediamine; diethylene-triamine and derivatives such aspentamethyldiethylenetriamine (PMDETA); pyridine and derivatives ofpyridine, such as bipyridine, 4-(N,N-dimethylaminopyridine (DMAP),picolines, lutidines, quinuclidines; imidazole and derivatives ofimidazole such as N-methylimidazole, N-ethylimidazole,N-propylimidazole, and N-butylimidazole.

Suitable metals for the substituent M above include copper, zinc, iron,nickel, cobalt, molybdenum, manganese, chromium, titanium, zirconium,hafnium, cadmium, mercury; and precious and rare earth metals such asrhodium, platinum, palladium, gold, silver, and iridium. A preferredmetal is zinc.

Particularly suitable metallasulfur derivatives for the method of thepresent invention are metallacyclosulfanes. Preferredmetallacyclosulfanes include those depicted below as A, B, C and D.Other metallasulfur derivatives are oligomeric or polymeric species andmay be linear as depicted in E below or branched as depicted in F belowwith the metal atoms serving as branch points.

Metallasulfur derivatives may contain charged ligand species. Forinstance, a suitable metallasulfur derivative for the formation of acyclododecasulfur compound is shown below:

It contains only sulfur atoms bonded to zinc in two metallacyclosulfanerings and two tetraphenyl phosphonium ion groups to neutralize thedianionic charge of the metallasulfur derivative.

A related metallasulfur derivative which contains ligands is illustratedbelow:

In this case a TMEDA ligand coordinated to zinc replaces a hexasulfidedianion, and thus the metallasulfur derivative is not anionic, it isneutral.

A particularly preferred class of metallacyclosulfanes for the method ofthe present invention are those containing an N-donor zinc complex. Evenmore particularly, when the intended cyclic sulfur allotrope iscyclododecasulfur, metallacyclosulfanes having four to six sulfur atomsand N-donor ligands coordinated to the zinc are preferred. Suchcomplexes are formed by reacting elemental sulfur, also referred toherein as cyclooctasulfur or S₈, with metallic zinc in a solventcomposed of, or containing, a donor amine, diamine or polyaminetemplating agent as described in more detail below. Examples ofN-donor-zinc-cyclosulfanes include (TMEDA)Zn(S₆), (DMAP)₂Zn(S₆),(pyridine)₂Zn(S₆), (methylimidazole)₂Zn(S₆), (quinuclidine)₂Zn(S₆),(PMDETA)Zn(S₄), and (bipyridine)₂Zn(S₆). The zinc complex,(TMEDA)Zn(S₆), is a particularly preferred metallacyclosulfane in themethod of the present invention and can be formed by reactingcyclooctasulfur, tetramethylethylenediamine and zinc. We have found thatthese metallacyclosulfane-forming reactions are best accomplished in thepresence of water, as in Example 14 in which the addition of waterconsistently produced (TMEDA)Zn(S₆) complex in high yields and purityeven with low grade TMEDA.

U.S. Pat. No. 6,420,581, the disclosure of which is incorporated hereinby reference in its entirety, relates to processes of producing zinchexasulfide amine complexes that are suitable for use according to thepresent invention. These processes comprise reacting zinc, sulfur and amolar excess of amine at an elevated temperature to obtain a reactionmixture comprising zinc hexasulfide amine complexes and excess amine. Afirst solvent in which the zinc hexasulfide amine complexes are largelynot soluble is added to obtain a slurry of the reaction mixture. Thezinc hexasulfide amine complexes may be recovered in a subsequentseparation process.

The metallasulfur derivatives of the method of the present invention maybe formed by reacting elemental sulfur with a sulfur templating agent.Accordingly, in a preferred embodiment, the method of the presentinvention includes the step of reacting elemental sulfur with a sulfurtemplating agent to form a metallasulfur derivative prior to the step ofreacting the metallasulfur derivative with an oxidizing agent.

Suitable sulfur templating agents for use in this embodiment of themethod of the present invention include those characterized by theformula:L_(x)M_(y)

-   -   wherein    -   L is a monodentate or polydentate ligand species which may be        the same or different when x>1;    -   x is the total number of ligand species L and is from 1 to 6        inclusive;    -   M is a metal atom; and    -   y is the total number of metal atoms and is from 1 to 4        inclusive.

The ligand species may be mono- or polydentate. Suitable ligand speciesare cyclopentadienyl or substituted cyclopentadienyl rings; amines suchas primary, secondary, and tertiary alkyl or aryl linear or cyclicamines and may also be diamines or triamines or other polyamines such asethylenediamine and ethylenetriamine and their derivatives, piperidineand derivatives, and pyrrolidine and derivatives; or heteroaromaticderivatives such as pyridine and pyridine derivatives or imidazole andimidazole derivatives.

Preferred amines include but are not limited to tetraalkylethylenediamines, such as tetramethyl ethylenediamine (TMEDA),tetraethyl ethylenediamine, tetrapropyl ethylenediamine, tetrabutylethylenediamine; diethylene-triamine and derivatives such aspentamethyldiethylenetriamine (PMDETA); pyridine and derivatives ofpyridine, such as bipyridine, 4-(N,N-dimethylaminopyridine (DMAP),picolines, lutidines, quinuclidines; imidazole and derivatives ofimidazole such as N-methylimidazole, N-ethylimidazole,N-propylimidazole, and N-butylimidazole.

Suitable metals for the substituent M above include copper, zinc, iron,nickel, cobalt, molybdenum, manganese, chromium, titanium, zirconium,hafnium, cadmium, mercury; and precious and rare earth metals such asrhodium, platinum, palladium, gold, silver, and iridium. A preferredmetal is zinc.

In the method of the present invention, the above-describedmetallasulfur derivative is reacted with an oxidizing agent. Anappropriate oxidizing agent is any agent which is reduced by ametallasulfur derivative and promotes the release of the sulfurcontained in the metallasulfur derivative. In addition, the oxidizingagent does not add sulfur from its composition to the cyclododecasulfurbeing produced in the process.

Non-limiting examples of such oxidizing agents include those of theformula:X—X′

wherein X and X′ are the same or different and are selected from thegroup consisting of halogens and pseudohaolgens. Preferably, X and X′are either both chlorine or bromine and accordingly the oxidizing agentfor the method of the present invention is either molecular bromine(Br₂) or molecular chlorine (Cl₂). X and X′ may also be pseudohalogengroups such as cyanide, thiocyanide, sulfate, thiosulfate, sulfonate orthiosulfonate. In the embodiment where the pseudohalogen groups arecyanide or thiocyanide, the oxidizing agent X—X′ would be dicyanogen ordithiocyanogen, respectively. In another embodiment wherein thepseudohalogen groups are sulfate, thiosulfate, sulfonate orthiosulfonate, it will be understood that the corresponding persulfateor perthiosulfate does not transfer sulfur atoms to thecyclododecasulfur being produced in the method of the present invention.

Another suitable oxidizing agent is molecular oxygen (O₂). Whenmolecular oxygen is the oxidizing agent X and X′ above are oxygen atoms.In the embodiment where the oxidizing agent is molecular oxygen, themolecular oxygen may, or may not, require the addition of a catalystwhich promotes and/or accelerates the rate of electron transfer from thesulfur in the metallasulfur derivative to the oxidant, such that theoxidizing agent may include molecular oxygen and a catalyst. Suchcatalysts may be metals or metal complexes and examples of suchcomplexes include the complexes of Fe(II), but other metals such asmanganese, vanadium, molybdenum and copper are also common. Anysubstance which, in combination with molecular oxygen, will induce thedesired oxidation of a metallasulfur derivative is within the scope ofcatalyst as described herein.

While the oxidizing agent for the method of the present invention hasbeen described above in the context of suitable chemical compounds, itwill be understood by a person of ordinary skill that, in general,electrochemically generated oxidants are capable of acting as oxidizingagents and may therefore be useful oxidizing agents in the method of thepresent invention. Examples include hydrogen peroxide, alkyl- and acylperoxides, halogen atom radicals, and high oxidation statemetal-centered oxidants such as Ce(IV) and Ir(V). Anodic oxidation ofmetallasulfur derivatives may include a catalyst at the anode to enablefacile and selective oxidation. Such species may be used in combinationwith or in conjunction with molecular oxygen as the oxidizing agent forthe method of the present invention.

Yet other suitable oxidizing agents include sulfuryl halides such asSO₂Cl₂ and SO₂Br₂ in which the SO₂ moiety is not incorporated into thecyclododecasulfur being produced by the method of the present invention.

In the method of the present invention, the stoichiometry of theoxidizing agent to the metallasulfur derivative may depend on thecomposition and structure of the metallasulfur derivative. In oneembodiment of the method of the present invention, the stoichiometricratio of the oxidizing agent to the metallasulfur derivative is selectedso that one equivalent of oxidizing agent (X—X′) is present for everytwo M-S bonds in the metallasulfur derivative. For the production of acyclododecasulfur compound, if the metallasulfur derivative has onemetal-sulfur bond for every three sulfur atoms then one equivalent of anoxidizing agent X—X′ may be combined with a weight of metallasulfurderivative equal to six equivalents of sulfur. Examples of suitableratios of oxidizing agent to metallasulfur derivative include: 1 mole of(TMEDA)Zn(S₆) to 1 mole of Br₂; 1 mole of (TMEDA)Zn(S₆) to 1 mole ofCl₂; 1 mole of (C₅H₅)₂Ti(S₅) to 1 mole of Cl₂; 1 mole of[PPh₄]₂[Zn(S₆)₂] to 2 moles of Br₂; 1 mole of [PPh₄]₂[Zn(S₆)₂] to 2moles of Cl₂; 1 mole of (N-methyl imidazole)₂Zn(S₆) to 1 mole of Br₂; 1mole of (N-methyl imidazole)₂Zn(S₆) to 1 of mole Cl₂; 1 mole of(PMDETA)Zn(S₄) to 1 mole of Br₂.

In another aspect of the method of the present invention, thestoichiometry of the oxidizing agent (X—X′) to the metallasulfurderivative may be selected so as to increase the purity of the finalcyclododecasulfur product. Thus, in a preferred embodiment, asubstoichiometric (i.e. less than one equivalent) ratio of the oxidizingagent to the metallasulfur derivative is selected in order to synthesizea cyclododecasulfur mixture having lower levels of halogens. In thisaspect, the stoichiometric ratio of the oxidizing agent to themetallasulfur derivative is selected so that less than one equivalent ofthe oxidizing agent is present for every two M-S bonds in themetallasulfur derivative. For the production of a cyclododecasulfurcompound, if the metallasulfur derivative has one metal-sulfur bond forevery three sulfur atoms then substoichiometric amounts of an oxidizingagent X—X′ may be combined with a weight of metallasulfur derivativeequal to six equivalents of sulfur. In this aspect, examples of suitableratios of oxidizing agent to metallasulfur derivative include: 1 mole of(TMEDA)Zn(S₆) to 0.90-0.99 mole of Br₂; 1 mole of (TMEDA)Zn(S₆) to0.90-0.99 mole of Cl₂; 1 mole of (C₅H₅)₂Ti(S₅) to 0.90-0.99 mole of Cl₂;1 mole of [PPh₄]₂[Zn(S₆)₂] to 1.80-1.99 moles of Br₂; 1 mole of[PPh₄]₂[Zn(S₆)₂] to 1.80-1.99 moles of Cl₂; 1 mole of (N-methylimidazole)₂Zn(S₆) to 0.90-0.99 mole of Br₂; 1 mole of (N-methylimidazole)₂Zn(S₆) to 0.90-0.99 mole Cl₂; 1 mole of (PMDETA)Zn(S₆) to0.90-0.99 mole of Br₂.

In one embodiment, the method of the present invention is a method forthe manufacture of a cyclododecasulfur compound. In this embodiment, apreferred metallasulfur derivative is atetramethylethylene-diamine/Zn(S₆) complex. Thetetramethylethylene-diamine/Zn(S₆) complex is most preferably formed insitu by reacting tetramethylethylenediamine and zinc in the presence ofelemental sulfur. Accordingly, in this embodiment, the templating agentis formed in situ in the presence of the elemental sulfur with which itreacts in the step for reacting the templating agent with the elementalsulfur.

According to the invention, cyclododecasulfur compound was formed inunexpectedly high yield by reacting one mole of thezinc-cyclohexasulfane (TMEDA)Zn(S₆) with one mole of oxidizing agent Br₂to form a theoretical ½ mole of cyclododecasulfur. Yields ofcyclododecasulfur approaching 70% or more based on the atoms of sulfurcontained in the initial reaction feed may be achieved. Such yields aremore than five times those achieved by methods described in the priorart. In another aspect, a substoichiometric (i.e. less than oneequivalent) ratio of the oxidizing agent to the metallasulfur derivativemay be selected in order to synthesize a cyclododecasulfur mixturehaving lower levels of halogens.

The method of the present invention may be performed at a wide range oftemperature, pressure, and concentration ranges. Suitable reactiontemperatures are from −78° to 100° C., or between −45° C. and 100° C.,more typically −10 to 40° C. In an embodiment wherein (TMEDA)Zn(S₆) isselected as the metallacyclosulfane and Br₂ is selected as thesulfur-free oxidizing agent in the manufacture of cyclododecasulfurcompound, typical reaction temperatures are from −78° C. to 60° C., orfrom −30° C. to 60° C., more preferably −10° C. to 40° C. In anembodiment wherein [PPh₄]₂[Zn(S₆)₂] is selected as themetallacyclosulfane and either Br₂ or Cl₂ as the oxidizing agent,typical reaction temperatures are from −78° C. to 60° C., or from −30°C. to 60° C., more preferably −10° C. to 40° C.

The metallasulfur derivative in the reacting step may be in any physicalform desirable to facilitate the reaction. Suitable forms include solid,slurry in an appropriate solvent, or solution in an appropriate solvent.Accordingly, in one embodiment of the method of the present invention,the method includes forming a slurry of the metallasulfur derivative ina solvent prior to the reacting step. In another embodiment of themethod of the present invention, the method includes forming a solutionof the metallasulfur derivative in a solvent prior to the reacting step.When a slurry or solution form is utilized, typical metallasulfurderivative concentrations for the slurry or solution are 0.5 to 30weight percent, more typically 2 to 25 weight percent, based on thetotal weight of the slurry or solution. Suitable solvents useful for theslurry or solution form in the reacting step include halogenatedsolvents of one to 12 carbon atoms and one halogen atom up toperhalogenated content. Examples of halogenated solvents includemethylene chloride, chloroform, carbon tetrachloride, carbontetrabromide, methylene bromide, bromoform, bromobenzene, chlorobenzene,chlorotoluenes, dichlorobenzenes, dibromobenzenes. Other suitablesolvents include alkanes of 5 to 20 carbons, aromatics, alkyl aromaticsof 7 to 20 carbons. Examples are pentanes, hexanes, cyclohexane,heptanes, octanes, decanes, benzene, toluene, xylenes, mesitylene, ethylbenzene and the like. One or more combinations of solvents may also beutilized.

Similarly, the oxidizing agent in the reacting step may be in anyphysical form desirable to facilitate the reaction. Preferably, theoxidizing agent is in the form of a dispersion in a suitable dispersant.Accordingly, in one embodiment of the method of the present invention,the method includes forming a dispersion of the oxidizing agent in adispersant prior to the reacting step. Typically, the oxidizing agentwill be present in the dispersion in an amount of 0.5 to 60 wt % basedon the total weight of the dispersion, more typically 1 to 25 wt % basedon the total weight of the dispersion. Examples of dispersants includemethylene chloride, chloroform, carbon tetrachloride, carbontetrabromide, methylene bromide, bromoform, bromobenzene, chlorobenzene,chlorotoluenes, dichlorobenzenes, and dibromobenzenes.

In the method of the present invention, the step of reacting themetallasulfur derivative with the oxidizing agent is typically initiatedand at least partially performed in a reaction zone. The reaction zoneis generally defined as the volume or space wherein the step of reactingthe metallasulfur derivative and the oxidizing agent commences and atleast partially progresses toward completion. As the method of thepresent invention may be performed as a batch or semi-batch operation orcontinuous operation, and in any mode or reactor format known in the artincluding plug flow and stirred tank reactor constructions, the reactionzone may be configured according to factors such as for example capacityexpectations; available manufacturing/plant area and capital; andutilities.

As the reaction of the reacting step is exothermic, the reacting steppreferably includes removing heat of reaction from the reaction zone. Inthe embodiment wherein one or more of the metallasulfur derivative andthe oxidizing agent are in a form that employs a solvent (slurry orsolution for the metallsulfur derivative, or dispersant for theoxidizing agent), the heat removal step may include operating the stepat a temperature and pressure to effect boiling of the solvent, solventsor dispersants. Alternatively, heat removal can be achieved by addingadditional solvent or reactants into the reaction zone or bytransferring heat from the reaction zone via a commercially availableand well-known external heat exchange device such as a shell and tube orspiral wound heat exchanger.

The method of the present invention may be performed as a batchoperation wherein reactants (metallasulfur derivative and oxidizingagent) are charged simultaneously or sequentially to the reaction zone.In one embodiment, wherein sequential addition of reactants is utilized,the reacting step of the method of the present invention may includefirst adding the oxidizing agent to the reaction zone then adding themetallasulfur derivative to the reaction zone. For sequential addition,the metallasulfur derivative may be in slurry or solution form and theoxidizing agent in dispersion form. In another embodiment, whereinsimultaneous addition of reactants is utilized, the reacting step of themethod of the present invention may include simultaneously adding theoxidizing agent and the metallasulfur derivative to the reaction zone.

Alternatively, the method of the present invention may be performed inplug-flow continuous mode, wherein reactants (metallasulfur derivativeand oxidizing agent) are charged as separate continuous streams in sucha manner to enhance mixing, such as impinging jets, into a static mixer,or a simple turbulent plug flow tubular reactor.

The reacting step of the present invention will typically extend for aperiod of from 30 seconds to 3 hours, preferably 1 minute to 2 hours andmore preferably 2 minutes to 1 hour. When (TMEDA)Zn(S₆) is utilized asthe metallasulfur derivative and Br₂ is utilized as the oxidizing agentin the manufacture of cyclododecasulfur, the reacting step of thepresent invention will typically extend for a period of from 1 minute to1 hour, or from 5 minutes to 20 minutes. When [PPh₄]₂[Zn(S₆)₂] isutilized as metallasulfur derivative and Cl₂ or Br₂ is utilized as theoxidizing agent, the reacting step of the present invention willtypically extend for a period of 1 minute to 1 hour, or from 1 minute to10 minutes.

The reacting step in the method of the present invention yields anS₁₂-containing reaction mixture. The reaction mixture typically containsthe cyclic sulfur allotrope as the desired product as well as one ormore of solvents, dispersants, reaction byproducts, and unreactedreactants, generally referred to herein as “impurities”, at least someof which may be insoluble in various solvents. Examples of by-productsand impurities include cyclooctasulfur and other allotropes of sulfursuch as cyclohexasulfur, cycloheptasulfur, and higher cyclosulfurderivatives; polymeric sulfur, either in amorphorous or crystallineforms; unreacted oxidizing agent; metallasulfur derivative and itspartially reacted derivatives or oligomers thereof; ligand, such asTMEDA; metals, such as zinc, from the metallasulfur derivativesynthesis; oxidant-sulfur derivatives, for example structures of theform X—Sn—X where X is Cl or Br and n is greater or equal to 1;metal-containing compounds, such as ZnBr₂, ZnCl₂, (TMEDA)ZnBr₂, and(TMEDA) ZnCl₂; and any solvents used in the reaction or isolation steps.

Accordingly, the method of the present invention may further includeprocesses for isolating S₁₂ from the S₁₂-containing reaction mixture.Suitable techniques, methods, and treatment steps for isolating thecyclododecasulfur from the cyclododecasulfur-containing mixture may varywidely depending on, for example, the choice of oxidizing agent,metallasulfur derivative, amount of unreacted reactants, thecorresponding reaction efficiency, yield, and the degree and the type ofimpurities and by-products and the like. The isolation process for S₁₂may thus comprise one or more of the following steps: dissolving,heating, drying, acid treating, solvent washing, crystallizing, andsedimentation. It is understood that the isolation process may involvemore than one of the same type of step. For example, an isolationprocess may comprise solvent washing, followed by dissolving,crystallization, a different solvent washing step, and drying.

Dissolving steps may include treating the S₁₂-containing mixture with asolvent for S₁₂ to form a dissolution liquor, followed by separating thedissolution liquor from insoluble impurities. Examples of impuritieswhich may be separated from the desired cyclododecasulfur in adissolution step include polymeric sulfur and other cyclic sulfurallotropes that exhibit low solubility in the solvent compared to S₁₂,metallasulfur derivatives, metals, and metal-containing compounds.Separating the dissolution liquor from insoluble impurities may utilizeseparation techniques known in the art, such as filtration,centrifugation, or sedimentation. Typically, separating the dissolutionliquor from insoluble impurities occurs at a temperature at or abovethat of the prior dissolution step to ensure that the dissolvedcyclododecasulfur remains dissolved during the separation operation.

Solvents utilized in the dissolving step are preferably chosen from thegroup consisting of alkanes, halogenated hydrocarbons, aromatics, andcarbon disulfide (CS₂). We note that the cyclododecasulfur obtainedaccording to the methods of the present invention exhibits solubilitiesin various solvents that depend, in part, on the temperature, and thatdiffer significantly from the solubility of cyclooctasulfur andpolymeric sulfur. For example, depending on temperature, cyclooctasulfuris 30 to 200 times more soluble than cyclododecasulfur, andcyclododecasulfur is at least an order of magnitude more soluble thanpolymeric sulfur, in p-xylene, chlorobenzene, and CS₂ (see Example 21).

Preferred dissolving solvents include those selected from the groupconsisting of CS₂, C₅ and larger alkanes, halogenated hydrocarbons ofone to 12 carbon atoms and one halogen atom up to perhalogenatedcontent. Examples of halogenated solvents include methylene chloride,chloroform, carbon tetrachloride, carbon tetrabromide, methylenebromide, bromoform, bromobenzene, chlorobenzene, chlorotoluenes,dichlorobenzenes, o-, m-, p-dibromobenzenes. Examples of alkane andaromatic dissolving solvents include o-, m-, p-xylenes, toluene,benzene, ethyl benzene, o-, m-, p-diisopropylbenzene, naphthalene,methyl naphthalenes, hexane and isomers, heptane and isomers,cyclohexane, methylcyclohexane, and decane.

We note that cyclododecasulfur exhibits relatively low solubility inmany solvents, so the dissolution step is typically performed at anelevated temperature to minimize solvent usage, typically above 20° C.up to about 140° C. The solubility varies considerably with the identityof the solvent, so the preferred temperature is dependent on the solventchosen. For example, when using CS₂ as the solvent for the dissolvingstep, a preferred temperature range is 30 to 90° C., or from 40 to 85°C. When using alkanes, halogenated hydrocarbons or aromatics as thesolvent for the dissolving step, a preferred temperature range is 75 to140° C., or from 90 to 125° C. The weight ratio of dissolving solvent tocyclic sulfur allotrope to be dissolved is typically about 500/1 to50/1, more typically 300/1 to 100/1.

We note that the most thermodynamically stable form of sulfur iscyclooctasulfur. Cyclosulfur allotropes (including S₁₂) and polymericsulfur are known to equilibrate to cyclooctasulfur upon heating to hightemperatures for undisclosed time periods. For example, at 141° C., theequilibrium composition of liquid sulfur is about 93 wt %cyclooctasulfur, with less than 0.5 wt % of any other individual C₁₀ toC₂₃ cyclosulfur allotrope (including 0.48 wt % S₁₂) and polymeric sulfur(see Steudel, R.; Strauss, R.; Koch, L., “Quantitative HPLC Analysis andThermodynamics of Sulfur Melts”, Angew. Chem. Int. Ed. Engl., 24(1),1985, pp. 59-60). Surprisingly, we have discovered that thisthermodynamic instability may be used to isolate certain cyclosulfurderivatives in a heating step. Thus, the thermal decomposition of thecyclododecasulfur obtained according to the methods of the presentinvention differs significantly from that of polymeric sulfur. Forexample, upon heating a mixture of polymeric sulfur andcyclododecasulfur in p-xylene at 115° C. for two hours, 100% of thepolymeric sulfur was decomposed to cyclooctasulfur, whereas less than 3%of the cyclododecasulfur was converted to cyclooctasulfur (see Examples22 and 23).

In the heating purification step of the present invention, theS₁₂-containing reaction mixture may be heated in the presence of asolvent to decompose and dissolve in the solvent at least some of theundesired impurities, including polymeric sulfur, present in theS₁₂-containing reaction mixture, producing a heating liquor andundissolved S₁₂. Preferably, S₁₂ is largely insoluble at the heatingtemperature, whereas cyclooctasulfur, the decomposition product of theundesirable cyclosulfur allotropes and polymer are soluble at theheating temperature.

This heating step may include a method to separate the heating liquorfrom the undissolved S₁₂. Separating the heating liquor from S₁₂ mayutilize separation techniques known in the art, such as filtration,centrifugation, or sedimentation. Typically, separating the heatingliquor from S₁₂ occurs at a temperature at or above that of the priorheating step to ensure that the impurities in the heating liquor remaindissolved during the separation operation. It is understood that S₁₂ maybe recovered from the heating liquor by an additional crystallizing stepin accordance with the present invention.

The time required for the heating step to achieve impurity decompositionis dependent on, for example, the solvent chosen and the temperature.Typically, the treatment may be accomplished effectively in 10 minutesto 4 hours, or from 15 minutes to 90 minutes.

The solvent utilized in this heating step is preferably chosen from thegroup consisting of alkanes, halogenated hydrocarbons, and aromatics.Preferred heating solvents are selected from the group consisting of C₅and larger alkanes, halogenated hydrocarbons of one to 12 carbon atomsand one halogen atom up to perhalogenated content. Examples ofhalogenated solvents include methylene chloride, chloroform, carbontetrachloride, carbon tetrabromide, methylene bromide, bromoform,bromobenzene, chlorobenzene, chlorotoluenes, dichlorobenzenes, o-, m-,p-dibromobenzenes. Examples of alkane and aromatic dissolving solventsare o-, m-, p-xylenes, toluene, benzene, ethyl benzene, o-, m-,p-diisopropylbenzene, naphthalene, methyl naphthalenes, hexane andisomers, heptane and isomers, cyclohexane, methylcyclohexane, anddecane.

The heating step is operated typically from about 70° C. to about 145°C., or from 80° C. to 130° C. The pressure used in the heating step isadjusted such that the solvent remains largely a liquid at the chosentemperature, typically pressures of about 1 bara to 20 bara. Thus thepressure preferably exceeds the vapor pressure of the solvent at thechosen temperature. More preferably the pressure is 1 bara to about 10bara.

The S₁₂-containing mixture may contain residual metal from preparationof the metallasulfur derivative, as well as metal-containing compoundssuch as the metallasulfur derivative itself, and any by-products of thereaction of the metallasulfur derivative with the oxidizing agent. Thismetal content may be removed by an acid treating step. In the acidtreating step of the present invention, the S₁₂-containing reactionmixture is contacted with an acid-containing solution, wherein the acidis one or more mineral acids, such as for example hydrochloric,hydrobromic, sulfuric, and phosphoric acids. The acids are typically indilute aqueous form, more typically 0.1 to 15 weight percent, or from 1to 8 weight percent in water.

The acid treating step is operated typically from about 0° C. to about80° C., or from about 10° C. to about 50° C. The time required for theacid treatment step may be accomplished effectively in 10 minutes to 4hours, or from 15 minutes to 120 minutes.

Sulfur allotropes are quite hydrophobic, and particles of suchsubstances tend to agglomerate in aqueous environments such as in theacid treatment step. To improve dispersion and enhance reactivity withthe acid solution, a small amount of dispersing agent may be added inthe contacting step, preferably added with the aqueous acid stream.Examples of suitable dispersing agents for the acid treatment step arewater miscible organics such as acetone, methanol, acetonitrile,ethylene glycol. Typical concentrations of the dispersing agent are 0.1to 15 weight percent, more typically 0.2 to 10 weight percent. Once theacid treating is completed, the acid-treated cyclosulfur allotrope ispreferably washed with neutral water to remove any residual acidcontent.

Solvent washing of the S₁₂ compound may be used to remove impuritieswith high solubility in the wash solvent, to displace another solvent,or to remove relatively small amounts of impurities of lower solubilityin the wash solvent. Said washing step is accomplished by contacting theS₁₂-containing reaction mixture with a washing solvent followed byseparating the S₁₂ from the washed mixture using known techniques suchas decantation, sedimentation, filtration, or centrifugation. Thewashing treatment typically does not completely dissolve the S₁₂, butrather removes impurities soluble in the washing solvent. Preferredwashing solvents include those selected from the group consisting ofCS₂, alkanes, halogenated hydrocarbons, C₃ to C₅ ketones, C₁ to C₃alcohols, C₂ to C₅ ethers, and aromatic solvents. Examples are o-, m-,p-xylenes, toluene, benzene, ethyl benzene, o-, m-,p-diisopropylbenzene, naphthalene, methyl naphthalenes, hexane andisomers, heptane and isomers, cyclohexane, methylcyclohexane, decane,chlorobenzene, bromobenzene, o-, m-, p-dichlorobenzene, methylenechloride, o-, m-, p-dibromobenzene-methanol, ethanaol, isopropanol,n-propanol, diethyl ether, methyl tert-butyl ether, benzene, acetone,methyl ethyl ketone. The weight ratio of washing solvent toS₁₂-containing mixture is typically about 0.1/1 to 3/1, more typically0.25/1 to 2/1.

During the crystallizing step, the amount of solvent present and thetemperature used may be selected so that any dissolved cyclooctasulfurand other undesirable impurities remain dissolved while the S₁₂ largelycrystallizes. When using CS₂ as the solvent, the crystallizing steppreferably includes cooling the dissolution liquor to a temperature offrom −30 to 25° C., more preferably from −10 to 10° C. When usingalkanes, halogenated hydrocarbons or aromatics as the solvent fordissolution, the crystallizing step preferably includes cooling thedissolution liquor to a temperature of from 0 to 80° C., more preferably10 to 60° C.

Particle size distribution of the S₁₂ crystals may be controlled to thedesired range by selecting the appropriate temperature, concentration,and rate of cooling. Rapid cooling and near-saturation concentrationstend to lead to more nucleation and smaller, more narrow particle sizedistribution. Slow cooling, with or without seed crystals, tends to leadto larger particles and a broader distribution of crystal sizes.

Once the S₁₂ is dissolved in a solvent, for example by the dissolving orheat treating steps of the present invention, the S₁₂ may be isolated inhigh purity by crystallizing from the solvent. The step of crystallizingdissolved S₁₂ to form S₁₂ crystals and a crystallization mother liquormay be accomplished by any means known in the art, such as coolingcrystallization, evaporative crystallization, anti-solventcrystallization, or combinations thereof. Seed crystals may also beadded to promote particle size growth and reduce excessive nucleation ifdesired. Cooling crystallization is a particularly preferred means ofcarrying the crystallizing step.

A preferred method of cooling crystallization for the isolation of S₁₂is cooling impinging jet crystallization, in which a hot S₁₂-ladendissolution liquor stream is brought into contact with an S₁₂-lean coolsolvent stream (comprising either the same solvent as the dissolutionliquor or a different solvent, or a mixture of solvents) at highvelocities in a confined mixing region. The small volume of the mixingregion and the high turbulence result in rapid cooling to a desiredequilibrated mixing temperature, high nucleation rates, and uniformparticle size distribution, an important characteristic of crystallineS₁₂ for vulcanization applications.

In one aspect, the particle size distribution of the crystalline S₁₂produced by a crystallizing step has a Dv(50) of 10 to 80 microns, witha Dv(90) less than 120 microns and a Dv(10) greater than 5 microns; morepreferably, the Dv(50) is 20 to 60 microns, with a Dv(90) less than 80microns and a Dv(10) greater than 10 microns.

The weight ratio of S₁₂-lean cool solvent stream to hot S₁₂-ladendissolution liquor stream used for impinging jet crystallization mayvary depending on the cool and hot stream inlet temperatures and thedesired equilibrated mixing temperature, but is typically from about10/1 to 0.5/1, more typically from 5/1 to 2/1.

When using alkanes, halogenated hydrocarbons, or aromatics as the coolor hot solvents for impinging jet crystallization, the preferred coolsolvent temperature is 40° C. to −30° C., or 30° C. to −10° C.; apreferred hot solvent temperature is 75 to 140° C., or from 90 to 125°C.; and the preferred equilibrated mixing temperature is 5° C. to 60°C., or 10° C. to 45° C. When using CS₂ as the cool or hot solvents forimpinging jet crystallization, the preferred cool solvent temperature is15° C. to −30° C., or 10° C. to −15° C.; the preferred hot solventtemperature is 35 to 75° C., or from 40 to 65° C.; and the preferredequilibrated mixing temperature is −5° C. to 25° C., or 0° C. to 20° C.

The impinging jet crystallizer is preferably designed such that thelinear velocities of the cool and hot streams are from 0.5 to 20 m/sec,from or 1 to 10 m/sec, and maintain turbulent flow in the hot stream,cold stream, and mixture stream.

Surprisingly, it has been discovered that differences in the density ofimpurities in the S₁₂-containing mixture and the S₁₂ itself may be usedto effect a purification of the S₁₂. In particular, S₁₂ may be separatedfrom metal particles, for example zinc particles. Thus, in asedimentation step, an S₁₂-containing mixture is contacted and mixedwith a sedimentation solvent, causing suspension of particles within thesedimentation solvent resulting in a suspended slurry mixture. Thesuspended slurry mixture is then subjected to an external field ofacceleration to effect a separation of types of particles into a settledparticle layer and a suspended particle mixture. The external field ofacceleration may be gravitational, centrifugal, magnetic, orelectrostatic in nature.

For example, in the embodiment of the present invention wherein a crudeS₁₂-containing mixture is produced from Br₂ oxidant and (TMEDA)Zn(S₆)metallasulfur derivative, the S₁₂-containing mixture may be subjected toa sedimentation step with chlorobenzene as the sedimentation solvent,forming a suspended slurry mixture. Agitation of the suspended slurrymixture is ceased, and the suspended slurry mixture is subjected tosimple gravity sedimentation, resulting in a settled particle layercomprising S₁₂ and large zinc particles, and a suspended particlemixture comprising mostly smaller zinc particles and sedimentationsolvent. Decantation of the suspended particle mixture away from theselected particle layer results in reduction of the zinc content of thesettled particle layer and enhancement of S₁₂ content.

The sedimentation step may be operated in batch or continuous mode andmay be repeated one or more times to enhance the separation. Preferredtemperatures for the sedimentation step are between 0 and 80° C., morepreferably 20 to 45° C.

The sedimentation solvent may comprise a liquid compound, dissolvedcyclooctasulfur, or other soluble impurities from the crudeS₁₂-containing mixture. Preferably the sedimentation solvent has adensity greater than 1 g/cc and less than about 1.8 g/cc at thesedimentation step temperature. Examples of useful liquid compounds foruse as a component of the sedimentation solvent are CS₂ and halogenatedhydrocarbons of one to 12 carbon atoms and one halogen atom up toperhalogenated content. Examples of halogenated solvents includemethylene chloride, chloroform, carbon tetrachloride, carbontetrabromide, methylene bromide, bromoform, bromobenzene, chlorobenzene,chlorotoluenes, dichlorobenzenes, o-, m-, p-dibromobenzenes. Thepresence of dissolved cyclooctasulfur in the sedimentation solventincreases the density of the sedimentation solvent and is favored, inparticular when suspending smaller metal particles. The preferred amountof dissolved cyclooctasulfur is dependent on the liquid compound usedand sedimentation temperature, but typically is from about 1 wt % toabout 20 wt %.

As the products of other steps of the isolation process, such asdissolving, heat treating, acid treating, solvent washing,crystallizing, and sedimentation, result in solvent-wetcyclododecasulfur crystals, the isolating process may optionally includea step of drying the solvent-wet cyclododecasulfur crystals to formdried sulfur allotrope crystals. Drying of the solvent-wetcyclododecasulfur crystals may be accomplished by means known in theart, such as by inert gas sweep, heating, placing under vacuum, orcombinations thereof. Typically, the drying step is accomplished attemperatures below the melting point of the cyclic sulfur allotrope,more typically from about 40° C. to about 110° C. at a pressure of lessthan 2 bara (bar absolute), typically at atmospheric pressure or down toabout 0.05 bara.

A preferred isolating process for the method of the present inventionincludes (i) dissolving the S₁₂ from the S₁₂-containing reaction mixtureby treating the S₁₂-containing mixture with a solvent for the S₁₂ toform a dissolution liquor, followed by separating insoluble impuritiesfrom the dissolution liquor; (ii) crystallizing the S₁₂ from thedissolution liquor to form S₁₂ crystals in a crystallization motherliquor, followed by separating the S₁₂ crystals from the crystallizationmother liquor; and (iii) drying of the mother-liquor-wet S₁₂ crystalsfrom the crystallizing step to produce a purified S₁₂ solid product.

In a second preferred embodiment, the isolating process includes (i)heating the S₁₂-containing reaction mixture in the presence of a solventto decompose and dissolve in the heating solvent at least some of theimpurities present in the S₁₂-containing reaction mixture and separatingthe remaining solids comprising the majority of the S₁₂ from a heatingliquor. Further steps in this embodiment preferably include one or moreof: (ii) contacting the solids separated in step (i) with acid; (iii)washing the acid from the solids-containing product of step (ii) with awater washing solvent; (iv) washing the water-washed, solids-containingproduct of step (iii) with a low boiling solvent; and (v) drying thewashed solids to produce a purified S₁₂ solid product.

In a third preferred embodiment, the isolating process includes (i)heating the S₁₂-containing reaction mixture in the presence of a solventto decompose and dissolve in the heating solvent at least some of theimpurities present in the S₁₂-containing reaction mixture, andseparating the remaining solids comprising the majority of the S₁₂ froma heating liquor. Further steps in this embodiment preferably includeone or more of: (ii) contacting the solids separated in step (i) with adissolving solvent to produce a dissolution liquor and insolubleimpurities; (iii) crystallizing S₁₂ from the dissolution liquor of step(ii) to produce S₁₂ crystals and a crystallization mother liquor; and(iv) drying the solvent-wet crystallized solids to produce a purifiedS₁₂ solid product.

In a fourth preferred embodiment, the isolating process includes (i)heating the S₁₂-containing reaction mixture in the presence of a solventto decompose and dissolve in the heating solvent at least some of theimpurities present in the S₁₂-containing reaction mixture, andseparating the remaining solids comprising the majority of the S₁₂ froma heating liquor. Further steps in this embodiment preferably includeone or more of: (ii) contacting the solids separated in step (i) with asedimentation solvent to produce a suspended slurry mixture and asettled particle layer; (iii) contacting the solids of the settledparticle layer separated in step (ii) with a dissolving solvent toproduce a dissolution liquor and insoluble impurities; (iv)crystallizing S₁₂ from the dissolution liquor of step (iii) to produceS₁₂ crystals and a crystallization mother liquor; and (v) drying thesolvent-wet crystallized solids to produce a purified S₁₂ solid product.

The following examples, while provided to illustrate with specificityand detail the many aspects and advantages of the present invention, arenot be interpreted as in any way limiting its scope. Variations,modifications and adaptations which do depart from the spirit of thepresent invention will be readily appreciated by one of ordinary skillin the art.

Analytical Methods

Differential Scanning Calorimetry (DSC)—

The differential scanning calorimetry method (DSC) to measure themelting point range of the cyclic sulfur allotrope compound involves afirst heating scan, from which are determined the melting peaktemperature(Tm1) and the exothermic peak temperature (Tex1). Theinstrument used was a TA's Q2000 DSC (RCS) with a refrigerated coolingsystem. The procedure used is described herein as follows. Theinstrument was calibrated according to the manufacturers “User'sManual”; by setting the onset of the melting point of adamantane, indiumand lead at −65.54° C., 156.60° C., and 327.47° C., respectively, andheat of fusion of Indium at 6.8 cal/g. A calibration specimen of about3.0 mg was then scanned at a rate of 20° C./min. in the presence ofhelium with a flow rate of 50 cc/min. For sulfur-containing specimens, asimilar method was used. A TA's Tzero aluminum pan and lid along withtwo aluminum hermetic lids were tared on a balance. About 3.0 mg of thesulfur-containing specimen was weighed into the Tzero pan, covered withthe tared lid, and crimped using a TA's sample crimper with a pair of“Black” dies. The crimped specimen from the “Black” die stand was movedto the “Blue” die stand, where two tared hermetic lids were placed onthe top of the specimen pan and crimped with the top “Blue” die. Anempty crimped Tzero aluminum pan and lid along with 2 hermetic lids wasprepared in a similar fashion as reference. The specimen and referencepans were placed in the DSC tray and cell at room temperature. After theDSC was cooled to −5° C. using a refrigerated cooling system, thespecimen was heated from −5 to 200° C. at a rate of 20° C./min in thepresence of helium. “Melt point onset” was defined as the temperature atthe start of the endothermic melting event. Data analysis was performedusing TA's software, Universal V4.7A, wherein, Tm1 refers to the lowmelting peak temperature occurring on the melting curve, using analysisoption, “Signal Maximum”. Tex1 refers to the exothermic peak temperatureoccurring right after Tm1, using analysis option, “Signal Maximum”.

UniQuant (UQ)—

Samples were also analyzed using X-ray fluorescence and the UniQuantsoftware package. UniQuant (UQ) is an x-ray fluorescence (XRF) analysistool that affords standardless XRF analysis of samples. Samples can thenbe semi-quantitatively analyzed for up to 72 elements beginning with rowthree in the periodic table (i.e. Na to higher Z). The data aremathematically corrected for matrix differences between calibrationstandards and samples as well as absorption and enhancement effects;i.e. inter-element effects. Some factors that can affect the quality ofresults include granularity in the sample (leading to shadow effects),mineralogical effects (due to sample inhomogeneity), insufficient samplesize, and lack of knowledge of the sample matrix. In cases where asample was amenable to both, the XRF UQ analysis and the ICP-OES (i.e.quantitative) analysis generally agree within +/−10%. Samples wereanalyzed for Zn, Br, Cl, and S content by UQ.

ICP—

Approximately 100 milligrams of sample was weighed into a precleanedQuartz sample tube. Then 3 mL of concentrated nitric acid was added toeach tube (Trace metal grade Fisher Chemical). Samples weremicrowave-digested using an Ultrawave Single Reaction Chamber DigestionSystem. After addition of scandium as an internal standard element (1ppm level after final dilution), digested samples were diluted to avolume of 25 mL, yielding a final acid concentration of ˜10% HNO3 (basedon nitric acid added and expected consumption of nitric acid during thedigestion). A 1 ppm scandium internal standard was added to each sample.A Perkin Elmer Optima 2100 ICP-OES instrument (PerkinElmer Inc., WalthamMass.) was calibrated with a matrix matched 1 ppm calibration standardand blank. Each sample, including a method blank was then analyzed forZn, S, Br, and Cl content.

X-Ray Diffraction (XRD)—Measurements were made on powder samples using aPANalytical Empyrean X-Ray Diffractometer (XRD) (Available fromPANalytical Incorporated). The XRD utilized a Copper anode X-Ray Sourceoperated at 45 kV and 40 mA. The system was configured for measurementsin the Bragg Brentano θ/2θ reflection geometry. Diffraction measurementswere collected from 5 to 80 degrees 2θ angle. The powder diffractionpatterns for crystalline sulfur allotropes were identified by comparisonto patterns from a purchased database (International Centre forDiffraction Data ICDD, Newtown Square, Pa., USA or equivalent) or topatterns of known reference standards. Quantitation of crystallinesulfur allotropes was performed by external calibration or the use ofReference Intensity Ratio (RIR) methodology.

Raman Spectroscopy—

The samples' Raman spectrum was measured using a Renishaw inVia confocalRaman microscope and WiRE 4.1 software with a 785 nm excitation laserand a 5× magnification microscope objective.

NMR—

Weigh approximately 0.0200 g of sample into a vial. Weigh approximately0.0200 g of the internal standard, 1,4-dimethoxybenzene, into the samevial. Add approximately 1 mL of pyridine-d5, or other deuterated solventthat the material is soluble in. Take a ¹H NMR of the material andintegrate the peak at δ 3.68 (6 protons). Integrate the two peaks at δ2.45 and δ 2.25 (16 protons). Calculate the % purity using the followingequation.% Purity=100[(mg IS/MW IS)*(∫sample/∫IS)*(6/16)*(MW sample/mg sample)]

IS=internal standard

MW=molecular weight

f=value of the integration from the ¹H NMR

Particle Size Distribution—

The particle size distribution of cycoldodecasulfur materials wasmeasured by a laser light scattering technique using a MalvernMastersizer 3000 instrument, capable of measuring a particle size rangefrom 0.1-1000 μm, equipped with optics comprising; a max. 4 mW He—Ne,632.8 nm red light source; nominal 10 mW LED, 470 nm blue light source;reverse Fourier (convergent beam) lens arrangement, effective focallength of 300 mm; with the detector in a log-spaced array arrangement,angular range of 0.015-144 degrees, and automatic alignment, Thedisperant (isopropanol) was added to the instrument and a small amountof cyclododecasulfur sample was added to the isopropanol to achieve alaser obscuration near 5%. The sample was mixed for 30 seconds to 60seconds, and subjected to light scattering analysis, with the particlesize distribution based on a Mie scattering model, using a refractiveindex of 1.93. The method reports volume-weighted diameters, with thefollowing distribution terms defined as:

D[4,3] is the “volume-weighted mean”, or “average” diameter, defined as:

${D\left\lbrack {4,3} \right\rbrack} = \frac{\sum{f_{i}*d_{i}^{4}}}{\sum{f_{i}*d_{i}^{3}}}$

where fi is the fraction of the particle having a diameter of di.

Dv (10)—10% of the population lies below this size

Dv (50)—The volume “median diameter”. 50% of the distribution above thisvalue and 50% below

Dv (90)—90% of the distribution lies below the size

Liquid Chromatrography—

The liquid chromatography (LC) method separates elemental sulfur speciesincluding S₈ and S₁₂. The sulfur species were identified by retentiontime determined from known samples. The quantity of S₈ was determined bycomparing the peak area of S₈ in the unknown sample with that of S₈standard solutions of known concentrations made in toluene. Thefollowing operating parameters apply to all LC analyses:

-   -   HPLC instrument: Agilent 1200 with quaternary pump and diode        array detector    -   Columns: Agilent, particle: Eclipse Plus C₁₈, particle size: 3.5        urn    -   Pre-column filter: Upchurch 0.5 urn stainless steel frit, part        no.: A316    -   Guard column: Phenomenex “security guard” HPLC guard cartridge        system with C₁₈ cartridge, part no.: KJO-4282    -   Autosampler vials: from VWR, catalog number 500 779    -   Flow rate: 0.8 mL/min    -   Run time: 40 min    -   Solvent: HPLC grade methanol isocratic    -   Column temperature: 6° C.    -   Detection wavelength: 254 nm, band width 16 nm Injection volume:        5 uL.

EXAMPLES

Preparation of a Cyclododecasulfur Compound from (TMEDA)Zn(S₆)

Example 1.

Preparation of metallasulfur derivative (TMEDA)Zn(S₆).Tetramethyl-ethylenediamine (TMEDA), (408 grams) and methanol (72 grams)were added to a 3 L, 3-neck glass flask equipped with a mechanicalstirrer (reaching closely to the vessel walls), thermocouple, N₂bubbler, water condenser, and electrical heating mantle. The system waspurged with nitrogen and the temperature of the mixture adjusted to 35°C. Freshly ground cyclooctasulfur (powder) was added over five minuteswhile maintaining stirring at 425-450 rpm. The temperature was increasedto 45° C. such that the freshly ground cyclooctasulfur was dissolved andwhereupon 40 grams of metallic zinc powder (<10 micron particlesize, >98% purity) was added over five minutes while maintainingstirring at 425-450 rpm. The gray-greenish yellow reactor contents werethen heated slowly to 86° C. and agitated for 4 hours, or until yellow.Once yellow, the mixture was held for an additional two hours attemperature, with agitation. At the end of the reaction time, the flaskwas cooled to room temperature, the agitator turned off, and free liquidremoved by vacuum extraction. Methanol (600 ml) was added to the flaskto create a slurry, and agitated for one hour. The resulting slurry wasthen filtered on a vacuum Buchner filter (1 micron paper) and washedwith two portions of 200 ml each of methanol. The solids were removedfrom the filter and dried overnight in a vacuum oven set at 50° C. and0.1 MPa. Yield was near quantitative, with 233 grams of metallasulfurderivative (TMEDA)Zn(S₆) complex, recovered at 97% purity as measured byNMR. Similar yields were uniformly achieved in multiple runs bycarefully controlling mixing conditions.

Preparation of a Cyclododecasufur Compound (S₁₂).

Methylene chloride (750 mL) was added to a 2 L, 4-neck glass flaskequipped with a mechanical stirrer, thermocouple, N₂ bubbler andstopper. Bromine (16.7 g, 104.5 mmol, 1.0 eq) as oxidizing agent wasweighed into a bottle containing 50 mL CH₂Cl₂ and this mixture was addedto the flask. The solution was cooled to 4° C. The zinc complex,(TMEDA)Zn(S₆), from Example 1, (97.5% pure) (40 g, 104.3 mmol, 1.0 eq),was added all at once and washed in with 50 mL CH₂Cl₂. There was animmediate exotherm to 11° C. The solution was stirred for 15 minutes,filtered, washed with cold CH₂Cl₂ and suctioned dry. The solids wereslurried in THF (250 mL), filtered and suctioned dry. The resultantsolids were slurried in cold CS₂ (150 mL), filtered and suctioned dry toafford 10.2 g of a pale yellow solid (yield 50.8% based on sulfur in thezinc complex). Evaluation using the UQ elemental analysis method showedthe material to be 96.6% sulfur (cyclododecasulfur compound (S₁₂) plussulfur polymer by Raman spectroscopy), 2.67% zinc and 0.7% bromine.

The cyclododecasulfur compound was further isolated in a two-vesselsystem comprising an upper 2 L, jacketed 3-neck glass flask equippedwith a mechanical stirrer, fine glass fritted filter plate,thermocouple, N₂ bubbler, dry ice trap, and bottom valve; and a lower 2L, jacketed 3-neck glass flask equipped with a mechanical stirrer,water-cooled condenser and 1 L glass receiver pot, thermocouple, N₂bubbler, dry ice trap, and bottom valve. To initiate the purificationprocedure, carbon disulfide (1200 grams) was added to the upper vesselalong with the cyclododecasulfur compound from the above reaction step(10.2 g). The contents of the flask were heated to 40-42° C. withstirring. After agitation of the mixture for half of an hour, the bottomvalve of the vessel was opened, and the free liquid pulled through thefritted glass filter into the lower flask. About half of the initialsolids remained on the filter. The solution in the second vessel wascooled to −6° C. over a period of 20 minutes or less. During the coolingphase, fine light yellow crystalline cyclododecasulfur compound formed.The solution was stirred for about 15 minutes at a final temperature of−6° C., whereupon the bottom valve of the vessel was opened and theslurry of S₁₂—CS₂ was dropped onto a Buchner funnel fitted with 2 micronfilter paper. The light yellow crystalline cyclododecasulfur compoundwas suctioned dry and scraped from the filter paper. The mother liquorfrom the final filtration was returned to the upper vessel, (containingresidual solids), along with makeup CS₂ to give 1200 grams of liquid.The upper vessel was agitated and heated again to 40-42° C. and thefiltering-cooling procedure was repeated to recover a second crop ofpurified cyclododecasulfur compound (S₁₂) crystals. After the finalheating-dissolution step, about 0.26 grams of greenish-yellow solidsremained on the upper fritted filter. The combined wet S₁₂ crystals wereplaced in a vacuum oven overnight at 30° C. and about 0.01 MPa to removeresidual CS₂, to give 9.3 grams of dried, purified cyclododecasulfurcompound. Evaluation by the UQ elemental method showed the material tobe at least 99.9% sulfur (all S₁₂ by Raman), and less than 100 ppm ofzinc and bromine. The melting point was determined first by DSC (20°C./min heating rate) and then using a thermal resistance melting pointapparatus to be 162° C. and 157° C. respectively. Overall yield ofsulfur to S₁₂ was 46%.

In examples 2 through 5, cyclododecasulfur compound was manufacturedusing the method of the present invention utilizing a single batch of(TMEDA)Zn(S₆) as the metallasulfur derivative, bromine as the oxidizingagent and a variety of dispersants and solvents.

Example 2

Methylene chloride as solvent for metallasulfur derivative anddispersant for the oxidizing agent. To a 2 L round bottom flask equippedwith a stir bar, nitrogen purge and cold water condenser, was added 900mL of methylene chloride. The flask was cooled in an ice bath. About 25mL of methylene chloride was added to a separate glass bottle and 18.29g of bromine weighed into the same bottle and this combination was addedto the round bottom flask and washed down with 25 mL of methylenechloride. Then 45.17 grams of (TMEDA)Zn(S₆) complex, (94% purity by NMR,prepared according to the method of Example 1) was added to the flaskand washed down with 50 mL of methylene chloride. The reaction wasstirred for 15 minutes and then filtered using a Buchner funnel and 1micron filter paper. The solids were then transferred to a second roundbottom flask and slurried with 400 mL of THF. This slurry was stirredfor 30 minutes and then filtered using a Buchner funnel and 1 micronfilter paper. The resulting solids were then transferred to yet anotherround bottom flask and cooled in an ice bath. 150 mL of ice-cooled CS₂was added to the third round bottom flask and stirred for 30 minutes.The mixture was then filtered using a Buchner funnel and 1 micron filterpaper. The resulting solids on the filter paper were vacuum dried toafford 11.42 g of a pale yellow crystal material (yield of 50.0% basedon sulfur in the zinc complex). Evaluation using the UQ elementalanalysis method showed the material to be 93.25% sulfur (highlyconcentrated in cyclododecasulfur compound (S₁₂) with traces ofcyclooctasulfur and sulfur polymer by Raman spectroscopy), 6.37% zincand 0.38% bromine.

Example 3

Chlorobenzene as solvent for metallasulfur derivative and dispersant foroxidizing agent. To a 1 L round bottom flask equipped with a stir bar,nitrogen purge and cold water condenser, was added 400 mL ofchlorobenzene. The flask was cooled in an ice bath. About 25 mL ofchlorobenzene was added to a separate glass bottle and 8.06 grams ofbromine weighed into the same bottle. This was added to the round bottomflask and washed down with 25 mL of chlorobenzene. Then 20 grams of(TMEDA)Zn(S₆) complex, (94% purity by NMR, from the same batch asExample 1) was added to the flask and washed down with 50 mL ofchlorobenzene. The reaction was stirred for 15 minutes and then filteredusing a Buchner funnel and 1 micron filter paper. The solids were thentransferred to a second round bottom flask and slurried with 200 mL ofTHF. This slurry was stirred for 30 minutes and then filtered using aBuchner funnel and 1 micron filter paper. The resulting solids were thentransferred to yet another round bottom flask and cooled in an ice bath.75 mL of ice-cooled CS₂ was added to the third round bottom flask andstirred for 30 minutes. The mixture was then filtered using a Buchnerfunnel and 1 micron filter paper. The resulting solids on the filterpaper were vacuum dried to afford 7.29 g of a pale yellow crystalmaterial (yield of 72% based on sulfur in the zinc complex). Evaluationusing the UQ elemental analysis method showed the material to be 95.58%sulfur (highly concentrated in cyclododecasulfur compound (S₁₂) withtraces of cyclooctasulfur and sulfur polymer by Raman spectroscopy),4.34% zinc and 0.08% bromine.

Example 4

p-Xylene as solvent for metallasulfur derivative and dispersant foroxidizing agent. To a 1 L round bottom flask equipped with a stir bar,nitrogen purge and cold water condenser, was added 450 mL of p-xylene.The flask was cooled in an ice bath. Then 20 grams of (TMEDA)Zn(S₆)complex, (94% purity by NMR, from the same batch as Example 1). 8.06grams of bromine were weighed into a small vial and transferred to anaddition funnel. Bromine was added slowly to the round bottom flask over15 minutes. After bromine addition, the reaction was stirred for anadditional 15 minutes and then filtered using a Buchner funnel and 1micron filter paper. The solids were then transferred to a second roundbottom flask and slurried with 200 mL of THF. This slurry was stirredfor 30 minutes and then filtered using a Buchner funnel and 1 micronfilter paper. The resulting solids were then transferred to yet anotherround bottom flask and cooled in an ice bath. 75 mL of ice-cooled CS₂was added to the third round bottom flask and stirred for 30 minutes.The mixture was then filtered using a Buchner funnel and 1 micron filterpaper. The resulting solids on the filter paper were vacuum dried toafford 6.85 g of a pale yellow crystal material (yield of 64.4% based onsulfur in the zinc complex). Evaluation using the UQ elemental analysismethod showed the material to be 92.37% sulfur (highly concentrated incyclododecasulfur compound (S₁₂) with traces of cyclooctasulfur andsulfur polymer by Raman spectroscopy), 6.85% zinc and 0.78% bromine.

Example 5

Methylene chloride as solvent for metallasulfur derivative anddispersant for oxidizing agent at reaction zone temperature of 15° C.Four liters of methylene chloride was added with stirring to a 12 literjacketed cylindrical flask, fitted with a mechanical agitator, funnel,cooling water condenser, nitrogen bubbler, and cooling bath. Bromine,100 grams, was added through the funnel and rinsed in with about 100 mLof methylene chloride. The contents of the flask were cooled to 15° C.Then 233.93 grams of (TMEDA)Zn(S₆) complex, (99% purity by NMR, preparedin a fashion as in Example 1) was added to the reactor via the funneland washed down with about 100 mL of methylene chloride. The reactorcontents were stirred for 15 minutes and filtered using a Buchner funnelwith 1 micron filter paper. About 3 L of THF was added to the flask andstirred for 30 minutes. The THF-washed solids were filtered using aBuchner funnel and 1 micron filter paper. The resulting THF-wet solidswere further washed on a Buchner funnel with 100 mL of CS₂. Theresulting solids on the filter paper were vacuum dried to afford 72.5grams of a pale yellow crystal material (yield of 62% based on sulfur inthe zinc complex). Evaluation using the UQ elemental analysis methodshowed the material to be 97.9% sulfur (highly concentrated incyclododecasulfur compound (S₁₂) with traces of cyclooctasulfur andsulfur polymer by Raman spectroscopy), 1.72% zinc and 0.37% bromine.

Preparation of Cyclododecasulfur from (N-Methylimidazole)₂Zn(S₆) Example6

Preparation of (N-methylimidazole)₂Zn(S₆). Zinc (7.06 g, 108 mmol, 1.0eq) and sulfur (20.86 g, 650 mmol, 6.02 eq) were stirred for 16 hours indry N-methylimidazole (155 mL) under N₂. The dark red solution wascooled to room temperature, diluted with 200 mL of ethyl ether and heldat 0° C. for 6 hours. The resulting solids were collected by filtrationand recrystallized from N-methylimidazole and ethyl ether to afford 18.5g of a bright yellow solid (40.3% yield). ICP showed 48.2% sulfur, 16.5%zinc, leaving 35.3% organic (calculated: 45.3% sulfur, 15.4% zinc, 38.7%organic). Quantitative NMR showed the material to be 97% pure.

Preparation of Cyclododecasulfur.

Bromine (6.03 g, 240 mmol, 1.0 eq) was added to 300 mL dichloromethanein a round bottom flask. The mixture was cooled to 1° C.(N-methylimidazole)₂Zn(S₆) was added all at once and washed in with 60mL dichloromethane. An exotherm to 7° C. was observed. The orange colordissipated after 10 minutes of stirring at which point the temperaturestarted to drop again. The solids were collected by filtration. Thematerial was slurried in THF, collected by filtration and slurried inCS₂. The solids were collected by filtration and suction dried to afford2.25 g of a pale yellow powder (31% yield). Raman showed the material tobe mostly cyclododecasulfur compound with some cyclooctasulfur. ICPshowed the material to be 88.9% sulfur, 7.7% zinc and 4.4% bromine.

Example 7

Preparation of [PPh₄]₂[Zn(S₆)₂]. Sodium sulfide nano-hydrate (6.4 g,26.7 mmol, 1.0 eq) and 160 mL water were added to a round bottom flaskunder nitrogen and purged well. Ground sulfur (2.33 g, 72.7 mmol, 2.72eq) was added and the mixture was heated to 50° C. for 30 minutes(slurry). Tetraphenylphosphonium chloride and 270 mL water were added toa separate round bottom flask under nitrogen, purged well and heated to50° C. for 30 minutes (almost all in solution). Thetetraphenylphosphonium chloride solution was added to the first flask.There was the immediate appearance of bright orange crystals. The newmixture was stirred at 50° C. for 2 hours. The solids were collected byfiltration and washed well with water. The crystals were re-slurried in400 mL water and stirred for 2 hours. The solids were again captured byfiltration and suction dried to afford 13.13 g of [PPh₄]₂[S₆] (100%yield based on sulfur).

Acetonitrile (100 mL) was added to a round bottom flask under nitrogenand purged well. [PPh₄]₂[S₆] (10 g, 11.5 mmol, 1.0 eq) and (TMEDA)Zn(S₆)(4.3 g, 11.5 mmol, 1.0 eq-99% purity by NMR) were added and washed inwith 50 mL acetonitrile. The solution turned dark blue when thephosphorus compound was added and bright yellow when the (TMEDA)Zn(S₆)compound was added. The mixture was stirred for 6 hours at roomtemperature. Ether (400 mL) was added. The resulting solids werecollected by filtration, washed with ether and suction dried to afford12.06 g of a bright mustard yellow solid. (93% yield). ICP showed 18.2%sulfur and 6.62% phosphorus (calculated 22% sulfur and 7.1% phosphorus).

Synthesis of Cyclododecasulfur.

Dichloromethane (100 mL) was added to a round bottom flask. Bromine(2.83 g, 17.7 mmol, 2.0 eq) in 50 mL dichloromethane was added.[PPh₄]₂[Zn(S₆)₂] (10 g, 8.86 mmol, 1.0 eq) was added all at once. Therewas an exotherm from 20° C. to 29° C. The bromine color disappearedimmediately. The mixture was filtered to remove solids that stronglyadhered to the filter paper and could not be removed. Yellow solidscrystallized out of the filtrate. The filtrate was concentrated on arotovap and the resulting solids were stirred overnight in methanol toremove impurities. The remaining solids were collected by filtration,washed with methanol and suction dried to afford 2.34 g of material (69%yield based on [PPh₄]₂[Zn(S₆)₂]). UQ showed the material to be 99.9%sulfur, 0.02% zinc and 0.05% bromine. Raman showed only acyclododecasulfur compound.

Example 8

Comparison of melting points of cyclododecasulfur materials. Severalbatches of purified cyclododecasulfur of the present invention wereprepared following the procedures exemplified by Examples 1 and 2. Eachfinal purified material was analyzed by Raman, Uniquat® or ICP, and themelt point onset temperature was measured using DSC as described above.The results are set forth in Table 8 below along with “control”cyclododecasulfur melt points extrapolated from reported data measuredat a DSC heat rate of 10° C./min, 5° C./min, and 2.5° C./min in Steudel,R.; Eckert, B., “Solid Sulfur Allotropes”, Topics in Current Chemistry(2003).

TABLE 8 sample melting point, ° C. invention batch 1 166.0 inventionbatch 2 156.0 invention batch 3 159.3 invention batch 4 158.6 inventionbatch 5 162.4 invention batch 6 164.0 invention batch 7 161.5 control153.5

As shown above, the cyclododecasulfur compound of the present inventionexhibits a melt point onset materially and unexpectedly higher thanprior art cyclododecasulfur compounds. Observed variations in melt pointfor the present invention were expected due to degree of impurities inthe samples as detected by Raman.

Example 9

Purification of Crude Cyclododecasulfur. Crude cyclododecasulfur wasprepared as in Example 1 from (TMEDA)Zn(S₆) complex and bromine wasfound to contain 1.9 wt % zinc and 0.5 wt % bromine by ICP, andcyclooctasulfur and polymeric sulfur by Raman. The melt point onsettemperature was measured as 132° C. using DSC as described above. Twograms of this crude cyclododecasulfur was added to 8 grams of p-xyleneand heated to 115° C., with mixing, for one hour. The remaining solidsthen allowed to settle to the bottom of the container and the liquid wasdecanted off, while maintaining the temperature at 115° C. The solidswere cooled to 50° C., and re-slurried with 15 grams of acetone, allowedto settle, and then the liquid was decanted off. The acetone slurry stepwas repeated two more times to ensure removal of p-xylene. A dilutesolution of aqueous hydrochloric acid was prepared by mixing 0.22 gramsof 37 wt % aqueous hydrochloric acid with 14.78 grams of demineralizedwater. The solid material from the acetone reslurry steps above wasmixed with the dilute aqueous hydrochloric acid and held at 40° C. forone hour. Several drops of acetone, equivalent to about 10% of the totalmixture, were added to the solids-hydrochloric acid mixture to preventaggregation and aid in dispersion of the sulfur material into thesolution. The vessel was vented to allow the escape of generated gases.After gas evolution stopped, the solids were allowed to settle and theliquid was decanted off. The remaining solids were slurried with 15grams of acetone, allowed to settle, and the liquid removed. The acetonewash step was repeated two more times. After the final decantation,additional acetone was removed by vacuum filtration on a Buchner funnelequipped with filter paper. The solids from the Buchner funnel werereslurried-settled-decanted twice, each time with 15 grams of carbondisulfide. After the final decantation, additional carbon disulfide wasremoved by vacuum filtration on a Buchner funnel equipped with filterpaper. The purified cyclododecasulfur material was dried at 40° C. undervacuum. After drying, a total of 1.55 g of purified cyclododecasulfurwas recovered at a yield of 78% of the original crude cyclododecasulfur.XRD showed no detectable cyclooctasulfur (detection limit of 1%), whileRaman showed no detectable cyclooctasulfur or polymeric sulfur. Ascalculated from ICP analysis, zinc and bromine levels in the purifiedcyclododecasulfur were reduced by 97% and 94% compared to the levels inthe original crude cyclododecasulfur. The melting point onsettemperature was found by DSC (20° C./min ramp rate) as 158.7° C.

Example 10

Purification of crude cyclododecasulfur by heating and crystallizingfrom para-xylene. Crude cyclododecasulfur was prepared as in Example 1,from (TMEDA)Zn(S₆) complex and bromine, and was found to contain 1.9 wt% zinc and 0.5 wt % bromine by ICP, and cyclooctasulfur and polymericsulfur by Raman. The melt point onset temperature was measured as 132°C. using DSC as described above. 7.53 grams of this crudecyclododecasulfur were added to a 1.5-liter jacketed glass vessel fittedwith a 1 micron glass frit plate in the bottom of the vessel, and amechanical agitator. 1504.45 grams of p-xylene were added to the frittedglass vessel and the mixture of crude cyclododecasulfur and p-xylene washeated to 115° C., with mixing, for thirty minutes. The contents of thevessel were pulled by vacuum through the fritted filter into a second1.0-liter jacketed glass vessel fitted with a mechanical agitator. Thecontents of the 1.0-liter vessel were cooled to 18° C., with agitation.As the solution cooled, a large crop of light yellow crystals was seento form. After a one-hour hold time, the slurry was drained onto afritted filter covered with 1 micron filter. The yellow crystals werefreed of liquid by vacuum filtration, and found to weigh 2.97 grams. Theheat treatment and recrystallization procedure described above werefound to produce cyclododecasulfur crystals of greater than 99.9% purityby UniQuant analysis. The solids from the filtration step were splitinto three fractions and each portion washed with either 20 grams ofcarbon disulfide, acetone, or p-xylene. The three washed samples weredried overnight at room temperature in a vacuum oven set at 0.017 MPa(absolute) and melting points were determined by DSC. Photomicrographsof each dried sample were taken to determine crystal habit and a roughparticle size range. Results are given in Table 10.

TABLE 10 DSC melt particle Wash Solvent Point, ° C. Crystal habit sizerange Carbon disulfide 162.0 agglomerates <150 micron Acetone 161.5 rods<100 micron p-xylene 161.6 rods <100 micron

Example 11

Purification of crude cyclododecasulfur by heating and crystallizingfrom chlorobenzene. Crude cyclododecasulfur was prepared as in Example1, from (TMEDA)Zn(S₆) complex and bromine, and was found to contain 1.9wt % zinc and 0.5 wt % bromine by ICP, and cyclooctasulfur and polymericsulfur by Raman. The melt point onset temperature was measured as 132°C. using DSC as described above. 7.47 grams of this crudecyclododecasulfur were added to a 1.5-liter jacketed glass vessel fittedwith a 1 micron glass frit plate in the bottom of the vessel, and amechanical agitator. 1499.7 grams of chlorobenzene were added to thefritted glass vessel and the mixture of crude cyclododecasulfur andchlorobenzene was heated to 115° C., with mixing, for thirty minutes.The contents of the vessel were pulled by vacuum through the frittedfilter into a second 1.0-liter jacketed glass vessel fitted with amechanical agitator. The contents of the 1.0-liter vessel were cooled to18° C., with agitation. As the solution cooled, a large crop of lightyellow crystals was seen to form. After a one-hour hold time, the slurrywas drained onto a fritted filter covered with a 1 micron filter. Theyellow crystals were freed of liquid by vacuum filtration, and found toweigh 3.75 grams. The heat treatment and recrystallization proceduredescribed above were found to produce cyclododecasulfur crystals ofgreater than 99.9% purity by UniQuant analysis. The solids from thefiltration step were split into three fractions and each portion washedwith either 20 grams of carbon disulfide, acetone, or chlorobenzene. Thethree washed samples were dried overnight at room temperature in avacuum oven set at 0.017 MPa (absolute) and melting points weredetermined by DSC. Photomicrographs of each dried sample were taken todetermine crystal habit and a rough particle size range. Results aregiven in Table 11.

TABLE 11 DSC melt particle Wash Solvent Point, ° C. Crystal habit sizerange Carbon disulfide 162.67 agglomerates <250 micron Acetone 161.03rods <100 micron Chlorobenzene 161.13 rods <100 micron

Example 12

Purification of cyclododecasulfur by heating, sedimentation of zinc, andcrystallizing. Four liters of chlorobenzene was added to a six-literjacketed glass processing vessel fitted with a pitch-blade mechanicalagitator, nitrogen purge, cooling water condenser, and heating bath forcirculation of temperature-controlled oil through the vessel jacket. Thecirculating oil bath was adjusted to bring the processing vessel to aninternal temperature of 115° C. Five hundred grams of crude S₁₂ asproduced in Example 17 below were added into the processing vessel whilestirring at about 300 rpm. The crude S₁₂ comprised 1.3 wt % Zn, 0.82 wt% Br, and the remainder S by Uniquant elemental analysis. The resultingslurry was maintained at 115° C. with stirring for 30 minutes. Theprocessing vessel was then cooled to room temperature (about 20° C.)while stirring.

Once at room temperature, the agitation was stopped and larger, densersulfur and zinc particles settled rapidly to the bottom of theprocessing vessel. Smaller, less dense, more buoyant, gray-green zincparticles settled slowly and largely remained suspended. The gray-greensupernatant with suspended zinc particles was removed from theprocessing vessel by vacuum suction. Care was taken to ensure that themain sulfur cake was largely undisturbed. The liquid removed from theprocessing vessel was passed through a 5 micron filter paper, depositinggray solids. The resulting filtrate was clear yellow in color. Theyellow filtrate was returned to the six-liter processing vesselcontaining the sulfur cake. At room temperature, agitation was startedto re-suspend the settled solids. Agitation was again stopped to allowsedimentation into a sulfur cake and a lighter gray-green supernatantwith suspended particles. This agitation/sedimentation/filtration cyclewas repeated 4 times until the resulting supernatant was no longergreenish, but clear yellow in color. The zinc-rich solids collected onthe filter were dried under vacuum overnight at 50° C. These driedsolids were found to weigh 23.8 grams.

When no more light zinc particles remained suspended in the supernatantupon settling, the agitation was started to re-suspend the settledsulfur-rich solids. The suspended sulfur-rich solids were pulled out ofthe processing vessel by vacuum and passed through a 5 micron filterpaper, depositing light yellow and gray solids. These solids werereturned to the processing vessel and four liters of pure chlorobenzenewere added. At room temperature, agitation was started to re-suspend thesettled solids. Agitation was stopped to allow sedimentation into adense gray zinc layer of heavy particles, with an upper layer of yellowsulfur particles, and a faint yellow supernatant with suspended sulfurparticles. The faint yellow supernatant with suspended sulfur particleswas removed from the processing vessel by vacuum suction. Care was takento ensure that the zinc layer was largely undisturbed. The liquidremoved from the processing vessel was passed through a 5 micron filterpaper, depositing yellow sulfur solids. The resulting filtrate wasreturned to the processing vessel. The agitator was started to re-slurrythe cake, and then stopped to allow settling of the heaviest zincparticles into a first zinc layer, with an upper layer of sulfur. Againsuspended sulfur particles were removed by vacuum and filtered, with thefiltrate returned to the processing vessel. Thisagitation/sedimentation/filtration cycle was repeated 5 times, graduallyremoving all of the sulfur particles until only a predominantly zinclayer remained. This final zinc layer was then removed from theprocessing vessel and was found to weigh 14.23 grams. The sulfur solidscollected on the filter were dried under vacuum overnight at 50° C.These dried solids were found to weigh 350.69 grams (70% recovery of theoriginal crude S₁₂ fed). Elemental analysis by the ICP method indicated0.61 wt % Zn, 0.12 wt % Br, and the remainder sulfur. Raman showed onlythe presence of cyclododecasulfur. Melting point was determined to be156.4° C. by DSC at a heat rate of 20° C./min.

The cyclododecasulfur product produced by the sedimentation step abovewas further processed by crystallization. 12 grams of thecyclododecasulfur was added to a 1.5-liter jacketed glass vessel fittedwith a 1 micron glass frit plate in the bottom of the vessel, and amechanical agitator. 1200 grams of chlorobenzene were added to thefritted glass vessel and the mixture of crude cyclododecasulfur andchlorobenzene was heated to 115° C., with mixing, for thirty minutes.The contents of the vessel were pulled by vacuum through the frittedfilter into a second 1.0-liter jacketed glass vessel fitted with amechanical agitator. The contents of the 1.0-liter vessel were cooled to18° C., with agitation. As the solution cooled, a large crop of lightyellow crystals was seen to form. After a 30-minute hold time, theslurry was drained onto a fritted filter covered with 1 micron filterpaper. The filtrate liquid was added back to the 1.5-liter vessel andreheated to dissolve additional S₁₂, followed by draining of thesupernatant into the 1-liter vessel, chilling to form crystals, andfiltration. This process was repeated until no more S₁₂ could bedissolved into the chlorobenzene. The combined crop of light yellowcrystals were freed of liquid by vacuum filtration and washed with 200grams of acetone. The washed sample was dried overnight at roomtemperature in a vacuum oven set at 0.017 MPa (absolute). The meltingpoint of the dried crystallized solids (10.0 grams) was determined byDSC as 159.5° C. The sample was found to be 99.85 wt % sulfur, 0.112 wt% Zn, and 0.0014 wt % Br by Uniquant.

Example 13

Purification of crude cyclododecasulfur by heating and crystallizingfrom chlorobenzene. Crude cyclododecasulfur from Example 17 (500 grams)was added to a 6-liter jacketed glass vessel fitted with a 1-micronglass frit plate in the bottom of the vessel, and a mechanical agitator.4400 grams of chlorobenzene were added to the fritted glass vessel andthe mixture of crude cyclododecasulfur and chlorobenzene was heated to115° C., with mixing, for thirty minutes. The contents of the vesselwere pulled by vacuum through the fritted filter into a second lower6.0-liter jacketed glass vessel fitted with a mechanical agitator. Thecontents of the lower 6.0-liter vessel were cooled to 18° C., withagitation. As the solution cooled, a large crop of light yellow crystalswas seen to form. After a one-hour hold time, the slurry was drainedonto a fritted filter covered with a 1-micron filter. The filtrate wasreturned to the upper vessel, reheated to 115° C. to dissolve more S₁₂,and dropped to the lower vessel, and cooled to 18° C. to produceadditional crystals. This process was repeated twenty times until nomore crystals were seen to form upon cooling of the lower vessel. Theyellow crystals on the fritted filter were freed of liquid by vacuumfiltration. The solids from the filtration step were washed withacetone. The washed sample was dried overnight at room temperature in avacuum oven set at 0.017 MPa (absolute). The dried sample was found toweigh 350.69 grams, with a melting point determined by DSC as 162.1° C.The sample was found to be greater than 99.9 wt % sulfur by Uniquant,and greater than 99% cyclododecasulfur by XRD analysis.

Example 14

Synthesis of (TMEDA)Zn(S₆) with or without water addition. Tetramethylethylenediamine (TMEDA), (2042 grams, 85 wt %, 99% pure, reagent plusgrade) and methanol (360 grams, 15 wt %) were added to a 6 L, 4-neckjacketed glass reactor equipped with a mechanical stirrer (reachingclosely to the vessel walls), thermocouple, N₂ bubbler, and watercondenser. The system was purged with nitrogen and the temperature ofthe mixture was adjusted to 22° C. Freshly ground cyclooctasulfur powder(673 grams, ˜90% pure) was added over a few minutes while maintaining astirring speed of 425-450 rpm. To this suspension, metallic zinc (207grams, 3.1 moles, <10 μm particle size, 98% pure) was added over fiveminutes while maintaining the same stirring speed. A brown solutionresulted with some greenish precipitate after heating the reactionmixture for 2 hours at 86° C. This indicated that the reaction failed toproduce the desired (TMEDA)Zn(S₆) complex. At this point, 78 g of waterwas added to the reaction and the resulting mixture was heated to 86° C.for an additional 2 hours and yellow precipitate of (TMEDA)Zn(S₆)formed. At the end of the reaction time, the flask was cooled to roomtemperature, the agitator was turned off, and free liquid was removed byvacuum extraction. Methanol (2000 ml) was added to the flask to createslurry and agitated for one hour. The resulting slurry was then filteredon a vacuum Buchner filter (1 micron paper) and washed with two portionsof 600 ml each of methanol. The solids were removed from the filter anddried overnight in a vacuum oven set at 50° C. and 0.1 MPa. Thecorresponding yield was near quantitative, with 1087 grams ofmetallasulfur derivative (TMEDA)Zn(S₆) complex, recovered at 97.5%purity as measured by NMR spectroscopy. Similar yields and purity wereuniformly achieved in multiple runs under same reaction conditions.Addition of water consistently produced (TMEDA)Zn(S₆) complex in highyields and purity even with low grade TMEDA.

Example 15

Large-scale synthesis of (TMEDA)ZnS₆— The following procedure andequipment were used produce eleven batches of (TMEDA)Zn(S₆). Details aregiven below for Batch 1, with reference to Table 15 for specificdifferences for the other ten batches. Tetramethyl ethylenediamine(TMEDA), (10590.0 grams, 99% pure, reagent plus grade), methanol (1869grams), and demineralized water (248 grams, 13.77 moles) were added to anitrogen-purged 22-liter, 316L stainless steel reactor equipped with amechanical pitched blade agitator, steam jacket, N₂ purge, and 2.54cm×30 cm 316L stainless steel water-jacketed condenser. Steam was addedto the reactor jacket to adjust the internal temperature to 25 celsiusand agitation was set at 250 rpm. Freshly ground cyclooctasulfur powder(2387 grams, 74.59 moles, obtained from grinding greater than 99% purecyclooctasulfur flake) was added over ten minutes while maintainingstirring at 250 rpm. Agitation was increased to 350 rpm and metalliczinc (734 grams, 11.23 moles, <10 μm particle size, 0.98% pure) wasadded over ten minutes while maintaining stirring at 350 rpm. Agitationwas increased to 375 rpm and the resulting mixture was then heatedslowly to 86° C. Vaporous material (mostly methanol) began to boil fromthe reactor at about 75° C., was condensed in the stainless steelcondenser and returned continuously to the reactor. The reactortemperature was maintained at 87.8° C., and the contents agitated at 375rpm for three hours. At the end of the reaction time, the reactor wascooled to room temperature, the agitator was set to 100 rpm, and thereactor contents were drained through the bottom valve of the reactorinto a polyethylene carboy. An additional four liters of fresh methanolwas added to the reactor, agitation was increased to 150 rpm, and thenthe reactor contents were drained into the same carboy. A 36 cm×36 cmmetal nutsche with a 5 micron polypropylene cloth, vacuum receiverflasks, and vacuum system was prepared to receive the crude(TMEDA)Zn(S₆) from the reaction step. The reaction effluent slurry wasagitated and poured onto the nutsche cloth surface and drained of liquidby filtration under vacuum (0.025 to 0.06 MPa). The solids on thenutsche were washed with approximately 40 liters of methanol to removeresidual TMEDA and unreacted sulfur. The washed solids were removed fromthe nutsche cloth, spread out on a large metal tray, and dried for 24hours in a vacuum oven set at 55° C. and 0.025 to 0.06 MPa. The weightof dried metallasulfur derivative (TMEDA)Zn(S₆) complex was determinedto be 3837.6 grams, recovered at 97.4% purity as measured by NMRspectroscopy. The molar yield on zinc metal was 89.2%. The averagepurity for batches 1-4 and 6-11 was 95.4%.

TABLE 15 Batch # 1 2 3 4 5 6 7 8 9 10 11 Sulfur form P P P P F P P P P PP Sulfur, grams 2387 2723 2724 2723 2723 2723 2723 2723 2723 2723 2723Zn dust, grams 734 837 837 837 837 837 837 837 837 837 837 TMEDA, grams10590 11313 11314 12020 12020 12020 12020 12020 12020 12020 12020 MeOH,grams 1869 2828 2828 2121 2121.3 2121 2121 2121 2121 2121.1 2121 Water,grams 248 282 282 282 282.1 282 282 282 282 282 282 Rxn time, hrs 3 3 33 4 3 3 3 3 3 3 Hold temp, ° C. 87.6 90 94 90.1 85.9 86.5 86.1 86.2 85.385 86.2 Product Mass, g 3837.6 3333.4 4313.4 4317.4 4318 4216.8 42584211.3 3975.1 4389.4 4214.9 NMR purity, 97.4% 94.0% 95.8% 96.4% 29.4%96.3% 96.4% 93.7% 95.6% 95.8% 93.2% wt % Zn Molar yield 89.2% 65.5%86.4% 87.1% 26.6% 84.9% 85.9% 82.5% 79.5% 88.0% 82.2% P = powder F =flake

Example 16

Large-scale preparation of cyclododecasulfur from bromine and(TMEDA)ZnS6 complex. A jacketed glass-lined 1893-liter steel reactorfitted with two pitched blade turbine impellers, glycol cooling fluid onthe jacket, nitrogen purge system, solids charging funnel, and pumpedaddition line was used to produce crude cyclododecasulfur from bromineand (TMEDA)ZnS₆ produced in Example 15. Chorobenzene (>99 wt % purity,355.3 kilograms) was charged to the reactor, stirred at 100 rpm, andcooled overnight to about −4.6° C. Dried Batches #1 (3776.3 grams), #2(3308.0 grams), #3 (4297 grams), and part of #4 (1900 grams) of(TMEDA)ZnS₆ prepared in Example 15 were added through the solidscharging funnel while maintaining agitation. An additional six kilogramsof chlorobenzene was poured through the solids funnel to wash residualsolids into the reactor. Agitation was increased to 150 rpm, andpreviously prepared chlorobenzene/bromine solution (60 kg chlorobenzene,5497.6 grams bromine, cooled to room temperature) was pumped into thereactor via the addition line over the course of one hour. During theaddition step, glycol cooling flow to the reactor jacket was maintained,and the reactor temperature rose to about 4.5° C., indicating reactionof the bromine with the (TMEDA)ZnS₆ complex. The reactor contents werestirred and cooled for 30 minutes, during which the reactor internaltemperature dropped to 2.0° C. The valve on the bottom of the reactorwas opened and the contents were gravity fed to a stainless steel basketcentrifuge (fitted with a 5-micron polypropylene filter cloth) forfiltration of the produced crude cyclododecasulfur solids. The1893-liter reactor was then charged with 420 liters of acetone tore-slurry any residual solids. This acetone slurry was then gravity fedto the centrifuge and passed through the solid cake of crudecyclododecasulfur crystals. The centrifuge cake was further washed with105 liters of acetone and centrifuged for additional three hours toremove residual liquids. The cake was removed, recovered from the filtercloth, and found to weigh 14.75 kg with a moisture content of 65.7%. Thewet solids were placed in stainless steel pans and dried for 17 hours ina vacuum oven at 50° C. and 0.067 MPa (absolute). The final weight ofdry crude cyclododecasulfur thus produced weighed 5.05 kg, with amoisture content of 0.33 wt %.

Example 17

Large-scale preparation of cyclododecasulfur from bromine and(TMEDA)ZnS₆ complex. A jacketed glass-lined 1893-liter steel reactorfitted with two pitched blade turbine impellers, glycol cooling fluid onthe jacket, nitrogen purge system, solids charging funnel, and pumpedaddition line was used to produce crude cyclododecasulfur from bromineand (TMEDA)ZnS₆ produced in Example 15. Chorobenzene (>99 wt % purity,711.5 kilograms) was charged to the reactor, stirred at 100 rpm, andcooled overnight to about −4.4° C. Dried Batches #6 through #11 of(TMEDA)ZnS₆ (25.2 kg), prepared in Example 15 were added through thesolids charging funnel while maintaining agitation. An additional sixkilograms of chlorobenzene was poured through the solids funnel to washresidual solids into the reactor. Agitation was increased to 150 rpm,and previously prepared chlorobenzene/bromine solution (120 kgchlorobenzene, 10.2 kilograms bromine, cooled to room temperature) waspumped into the reactor via the addition line over the course of onehour. During the addition step glycol cooling flow to the reactor jacketwas maintained, and the reactor temperature rose to about 3.0° C.,indicating reaction of the bromine with the (TMEDA)ZnS₆ complex. Thereactor contents were stirred and cooled for 20 minutes, during whichthe reactor internal temperature dropped to 2.0° C. The valve on thebottom of the reactor was opened and the contents were gravity fed to astainless steel basket centrifuge (fitted with a 5-micron polypropylenefilter cloth) for filtration of the produced crude cyclododecasulfursolids. The 1893-liter reactor was then charged with 840 liters ofacetone to re-slurry any residual solids. This acetone slurry was thengravity fed to the centrifuge and passed through the solid cake of crudecyclododecasulfur crystals. The centrifuge cake was further washed with212 liters of acetone and centrifuged for an additional five hours toremove residual liquids. The cake was removed, recovered from the filtercloth, and found to weigh 12.9 kg with a moisture content of 27.6%. Thewet solids were placed in stainless steel pans and dried for 24 hours ina vacuum oven at 50° C. and 0.067 MPa (absolute). The final weight ofdry crude cyclododecasulfur thus produced weighed 9.35 kg, with amoisture content of 0.30 wt %.

Example 18

Preparation of (TMEDA)Zn(S₆) with addition of water. Tetramethylethylenediamine (TMEDA), (2042 grams, 85 wt %, 99% pure, reagent plusgrade), methanol (360 grams, 15 wt %), and water (78 grams) were addedto a 6 L, 4-neck jacketed glass reactor equipped with two mechanicalpitched blade agitators (reaching closely to the vessel walls),thermocouple, N₂ bubbler, and water condenser. The system was purgedwith nitrogen and the temperature of the mixture was adjusted to 22° C.Freshly ground cyclooctasulfur powder (673 grams, greater than 99% pure)was added over five minutes while maintaining a stirring speed of425-450 rpm. To this suspension, metallic zinc (207 grams, 3.1 moles,<10 μm particle size, ≥98% pure) was added over five minutes whilemaintaining the same stirring speed. The greenish yellow mixture wasthen slowly heated to 86° C. and agitated for 2 hours, or until yellowprecipitate appeared. Once the color turned yellow, the mixture washeated with stirring for an additional one hour. At the end of thereaction time, the flask was cooled to room temperature, the agitatorwas turned off, and free liquid was removed by vacuum extraction.Methanol (2000 ml) was added to the flask to create slurry and agitatedfor one hour. The resulting slurry was then filtered on a vacuum Buchnerfilter (1 micron paper) and washed with two portions of 600 ml each ofmethanol. The solids were removed from the filter and dried overnight ina vacuum oven set at 50° C. and 0.1 MPa. The corresponding molar yieldon zinc metal was 90.1%, with 1087 grams of metallasulfur derivative(TMEDA)Zn(S₆) complex recovered at 98% purity as measured by NMRspectroscopy. Similar yields and purity were uniformly achieved inmultiple runs under same reaction conditions.

Example 19

Preparation of cyclododecasulfur compound (S₁₂) using chlorine (Cl₂) asan oxidizing agent. Chlorobenzene (25 mL) was added to a 100 mL, 3-neckglass flask equipped with a stir-bar, thermocouple, N₂ bubbler andstopper. To this flask, the zinc complex, (TMEDA)Zn(S₆) (2.12 g, 5.53mmol, 97.5% pure) was added and the resulting slurry was cooled to 0° C.using an ice-water bath. Next, a stoichiometric amount of chlorine (1Msolution in chlorobenzene, 5.5 mL, 5.53 mmol, 1.0 eq) was introduced tothe flask and the resulting mixture was stirred for 15 minutes,filtered, washed with chlorobenzene and suctioned dry. The solids wereslurried in THF (200 mL), filtered, and suctioned dry. The resultantsolids were slurried in cold CS₂ (50 mL), filtered and suctioned dry toafford 0.65 g of a pale yellow solid (yield 61.3% based on sulfur in thezinc complex). Evaluation using the X-ray diffraction (XRD) method andRaman Spectroscopy showed a mixture containing cyclododecasulfur,cyclooctasulfur, and polymeric sulfur species.

Example 20

Preparation of halide-free cyclododecasufur compound (S₁₂) with asubstoichiometric amount of bromine (Br₂) as an oxidizing agent.Chlorobenzene (300 mL) was added to a 1 L, 4-neck glass flask equippedwith a magnetic stir-bar, dropping funnel, N₂ bubbler and stopper. Tothis flask, the zinc complex, (TMEDA)Zn(S₆) (30.07 g, 75.98 mmol, 94.5%pure) was added and the resulting slurry was cooled to 0° C. using anice-water bath. Bromine (3.85 mL, 74.46 mmol, 0.98 eq) as oxidizingagent was charged into the dropping funnel containing 50 mLchlorobenzene and this solution was dropwise added to the flask over aperiod of −15 minutes. The solution was stirred for 15 minutes,filtered, washed with chlorobenzene to remove residual zinc complex andsuctioned dry. The solids were slurried in THF (500 mL), filtered, andsuctioned dry. The resultant solids were slurried in cold CS₂ (200 mL),filtered and suctioned dry to afford 10.4 g of a pale yellow solid(yield 71.1% based on sulfur in the zinc complex). Evaluation using theUQ elemental analysis method showed the material to be 99.9% sulfur(cyclododecasulfur compound (S₁₂) plus sulfur polymer by Ramanspectroscopy) and 148 parts per million (ppm) zinc. Nobromine-containing impurity was detected by UQ elemental analysis.

Example 21

Solubility of cyclooctasulfur, cyclododecasulfur, and crystallinepolymeric sulfur in carbon disulfide, chlorobenzene, and para-xylene.Fifty grams of p-xylene was added to each of three identical100-milliliter jacketed glass vessels fitted with a circulating heatingbath, cooling water condenser, magnetic stir bar and stir plate, andnitrogen purge. All vessels were heated to the desired temperature, andcyclooctasulfur, cyclododecasulfur (prepared as in Example 2), andunoiled commercial crystalline polymeric sulfur (Crystex™) was added insufficient quantities to each of the glass vessels to allow undissolvedsolids to remain after dissolution and equilibration of the mixture. Theequilibration period typically lasted 2 to 8 hours, during which thecontents of the vessel were maintained at the desired temperature andstirred continuously. Upon equilibration, supernatant liquid waswithdrawn from the vessels via a heated fritted glass pipette (heated tothe same temperature as the solution). The supernatants were analyzed byUniquant to determine sulfur content, indicating the solubility of thesulfur species at the vessel temperature. Similar experiments wereconducted for carbon disulfide and chlorobenzene for each of the threesolutes. Solubilities in weight % of solute in each solvent aresummarized in Table 21.

TABLE 21 Temper- Cyclo- Cyclo- Polymeric Solvent ature, ° C. octasulfurdodecasulfur Sulfur P-xylene 22 2.3 wt % Not measured BDL* 45 5.6 wt %<0.05 wt %  BDL* 115 18.7 wt %  0.4 wt % Decomposes to S₈ Cl-benzene 222.4 wt % Not measured BDL* 45 6.2 wt % 0.015 wt %  BDL* 115 21.7 wt % 0.44 wt %  Decomposes to S₈ CS₂ 22  32 wt % 0.2 wt % BDL* 45  48 wt %0.5 wt % BDL* *BDL = below detection limit

Example 22

Thermal decomposition of crystalline polymeric sulfur in p-xylene. Thepurpose of this experiment was to determine the rate that polymericsulfur thermally decomposes into cyclooctasulfur in p-xylene. Polymericsulfur is essentially insoluble in p-xylene, except when the polymerdecomposes into cyclooctasulfur. Thus, the sulfur content in thep-xylene is a measure of the amount of polymeric sulfur that hasdecomposed to cyclooctasulfur. In this experiment, 50.32 grams ofp-xylene were added to a 100-milliliter jacketed glass vessels fittedwith a circulating heating bath, cooling water condenser, magnetic stirbar and stir plate, and nitrogen purge. The p-xylene was heated to 115°C. and 2.03 grams of unoiled commercial crystalline polymeric sulfur(Crystex™) was added while stirring. Periodically samples of thesupernatant liquid were withdrawn from the vessel via a heated frittedglass pipette (heated to the same temperature as the solution). Thesesupernatant samples were analyzed by Uniquant to determine sulfurcontent. The sulfur content was used to calculate the amount ofpolymeric sulfur remaining undissolved and undecomposed tocyclooctasulfur. After 60 and 75 minutes at 115° C., about 85% andessentially 100% respectively, of the polymeric sulfur had beenconverted into cyclooctasulfur.

Example 23

Thermal decomposition of cyclododecasulfur in p-xylene. The equipmentand procedure used in Example 22 for measurement of the decomposition ofpolymeric sulfur was used to measure the decomposition ofcyclododecasulfur in para-xylene. Two grams of purifiedcyclododecasulfur (produced by a procedure in the fashion of Example 2)was heated and stirred in 50.0 grams of p-xylene in a 100-milliliterjacketed glass vessels fitted with a circulating heating bath, coolingwater condenser, magnetic stir bar and stir plate, and nitrogen purge.After 60, 75, and 120 minutes at 115° C., the content of sulfur in thep-xylene solvent was found by Uniquant to be about 0.4 wt % in eachcase, similar to the solubility of cyclododecasulfur in p-xylene at 115°C. (see Example 21). Upon cooling of the p-xylene, filtration, anddrying of the recovered solids overnight in a vacuum oven at roomtemperature and 0.067 MPa (absolute), greater than 97% of thecyclododecasulfur input weight of solids was recovered. This materialhad a melting point of 161° C. by DSC, indicating high puritycyclododecasulfur product.

Example 24

Oxidation of (TMEDA)ZnS₆ by O2. O2 gas was bubbled into a suspension of(TMEDA)ZnS₆ (1.0 mmol) in water (30 mL) in the presence of ethylenediamine (4.0 mmol) at room temperature for 4 hours, resulting in a lightyellow suspension. The suspension was filtered and washed with H₂O,acetone, and dichloromethane, and then dried in air to give acyclododecasulfur-containing reaction mixture comprisingcyclohexasulfur, cyclooctasulfur, and cyclododecasulfur, at a 50% sulfuryield.

Example 25

Oxidation of (TMEDA)ZnS₆ by H2O2. H2O2 (34 wt % in water) was addeddropwise over 30 minutes to a suspension of (TMEDA)ZnS₆ (1.0 mmol) inwater (30 mL) in the presence of ethylene diamine (4.0 mmol) at roomtemperature for 4 hours, resulting in a light yellow suspension. Thesuspension was filtered and washed with H₂O, acetone, anddichloromethane, and then dried in air to give acyclododecasulfur-containing reaction mixture comprisingcyclohexasulfur, cyclooctasulfur, and cyclododecasulfur, at a 70% sulfuryield.

Example 26

Oxidation of (TMEDA)ZnS₆ by SO₂Cl₂. SO₂Cl₂ (6.0 mmol) was added dropwiseover 60 minutes to a suspension of (TMEDA)ZnS₆ (3.0 mmol) indichloromethane (40 mL) at −78° C. The resulting solution was stirredfor an additional hour at −78° C. Upon warming to 0° C. a light yellowsuspension formed. The suspension was quenched with 5 ml of 1M HCLsolution in 15 ml of H₂O. The quenched solution, was filtered and washedwith H₂O, acetone, and dichloromethane, and then dried in air to give acyclododecasulfur-containing reaction mixture comprisingcyclododecasulfur, at a 40% sulfur yield.

Example 27

Purification of crude cyclododecasulfur by crystallizing fromchlorobenzene. Crude cyclododecasulfur from Example 17 was heat treatedand subjected to zinc sedimentation as in Example 12. This partiallypurified material was subjected to continuous dissolving and coolingcrystallizing steps from chlorobenzene solvent to produce a purified S₁₂product. The continuous dissolving-crystallizing apparatus comprised thefollowing in counterclockwise flow order: a 15-liter jacketed glassdissolving vessel (steam heated) fitted with a 5 micron filter papercovered by a stainless steel screen and supported on a perforated Teflonplate in the bottom of the vessel, a mechanical agitator, cooling watercondenser, upper solvent inlet port, and bottom flow valve; centrifugalpump (maximum 23 liter/min maximum flow rate); a cartridge filter fittedwith a spiral wound glass-baked fiber element (0.75 micron, 0.046 m²area); a shell in tube heat exchanger comprising 20 meters of coiled1.25 cm nominal diameter stainless steel tubing (process side) in a 5 cmstainless steel shell (cooling fluid side−chilled water coolant); a bagfilter and housing fitted with 5 micron 0.1 m² area polypropylene wovenfilter; a 4 liter stainless steel mother liquor tank; a centrifugal pump(maximum 23 liter/min maximum flow rate); a shell in tube heat exchangercomprising 20 meters of coiled 1.25 cm nominal diameter stainless steeltubing (process side) in a 5 cm stainless steel shell (heating fluidside−steam heating); with outlet from the hot exchanger returning to thedissolving tank. All tubing connecting the dissolving vessel, cartridgefilter, hot exchanger up to the process inlet of the cold exchanger wasfitted with electrical heating tape to maintain the desired dissolutiontemperature. All tubing connecting the cold exchanger, mother liquortank, to the inlet of the hot exchanger was fitted with foam insulationto maintain the desired dissolution temperature. Both the process fluidand inlet chilled water flow entered the cold exchanger at the top ofthe vessel (in tube and shell side respectively) to give co-currentflow.

The dissolving tank was charged with 15 liters of chlorobenzene, solventcirculation was started at 5.4 liters/min. The steam flow to the hotexchanger and dissolving vessels and heat tapes were adjusted tomaintain an average temperature of 106.5° C. at the process fluid inletto the cold exchanger throughout the experiment. Chilled water flow wasadjusted to maintain the process side outlet temperature of the coldexchanger at an average of 24.7° C. throughout the experiment. Onceequilibrium temperatures as described above were reached in the processfluid loop, 50 grams of feed material (partially purified S₁₂ asdescribed above) was added to the dissolving vessel, producing a yellowgreen slurry mixture. Within five minutes, light yellow crystals wereseen to be collecting in the bag filter. After an additional 5-10minutes, the dissolving tank became clear, indicating removal of S₁₂ anddark gray-green solids were seen on the filter paper. An additional 51gram charge of feed material was added to the dissolving tank and theprocess repeated until the dissolving tank became clear again.Additional 50 gram charges of feed material were added and processed fora total charge of 302.34 grams. The flows were stopped and light yellowcrystals emptied from the bag filter. Solvent-wet S₁₂ solids from thebag filter were washed with acetone to remove chlorobenzene and driedovernight at room temperature in a vacuum oven set at 0.017 MPa(absolute). The melting point of the dried S₁₂ crystalline product (243grams) was determined by DSC as 162.1° C., with a purity greater than99.9 wt % sulfur by Uniquant, with a Dv(50) of 41 microns by PSDanalysis.

Example 28

Purification of crude cyclododecasulfur by impinging jet coolingcrystallizing from chlorobenzene. Crude cyclododecasulfur was purifiedby a heat treating step as in Example 13, and was further processed inan impinging jet cooling crystallizing step to produce tailored particlesize cyclododecasulfur crystals. The impinging jet apparatus comprisedtwo agitated hot and cold glass jacketed 4-liter vessels, gear pumps forpumping fluid, a stainless steel impinging jet tee (dimensions: 2 mminside diameter cool fluid inlet, 2 mm inside diameter hot fluid inlet,5 mm outlet tubing), 1 micron filter paper on a fritted glass plate, anda glass filtrate collection vessel.

In a first experiment, 4.5 grams of heat-treated S₁₂ was dissolved in1650 grams of chlorobenzene in the hot vessel at 110° C. The cold vesselwas filled with chlorobenzene and chilled to −20° C. Once the S₁₂ haddissolved flow was started to the impinging jet tee at rate of 180ml/min hot fluid and 360 ml/min cold fluid. Small light yellow crystalswere observed to form immediately in the impinging jet outlet stream,and were filtered out on the 1 micron paper, and mother liquor collectedin the filtrate tank. The outlet mixture stream of the impinging jet wasfound to have a temperature of 23° C. Solvent-wet S₁₂ solids from thefilter paper were washed with acetone to remove chlorobenzene and driedovernight at room temperature in a vacuum oven set at 0.017 MPa(absolute). The dried crystals (4.1 grams) were submitted for particlesize distribution. A second experiment was complete at identicalconditions except changing the cold fluid flow to 540 ml/min. Outlettemperature was 12.5° C., with a dry crystal recovery of 4.2 grams.Results are given in Table 28 for both experiments.

TABLE 28 Experiment 1 Experiment 2 Cold/hot flow ratio 2/1 3/1 Coldlinear vel, m/s 1.91 2.86 Hot linear vel, m/s 0.95 0.95 Outlet T, ° C.23.3 12.5 D[4, 3], microns 80.9 35.9 Dv(10), microns 25.2 12.8 Dv(50),microns 66.9 31.7 Dv(90), microns 145 65.3

The foregoing description of various embodiments of the invention hasbeen presented for purposes of illustration and description. It is notintended to be exhaustive or to limit the invention to the preciseembodiments disclosed. Numerous modifications or variations are possiblein light of the above teachings. The embodiments discussed were chosenand described to provide the best illustration of the principles of theinvention and its practical application to thereby enable one ofordinary skill in the art to utilize the invention in variousembodiments and with various modifications as are suited to theparticular use contemplated. All such modifications and variations arewithin the scope of the invention as determined by the appended claimswhen interpreted in accordance with the breadth to which they arefairly, legally, and equitably entitled.

The invention claimed is:
 1. A method for the manufacture of cyclododecasulfur, comprising reacting a metallasulfur derivative with an oxidizing agent in a reaction zone to form a cyclododecasulfur-containing reaction mixture containing cyclododecasulfur, wherein the oxidizing agent is characterized by the formula: X—X′ wherein X and X′ are the same or different and are selected from the group consisting of halogens or pseudohalogens.
 2. The method of claim 1 wherein the metallasulfur derivative is characterized by the formula:

wherein L is a monodentate or polydentate ligand species which may be the same or different when x>1; x is the total number of ligand species and is from 0 to 6 inclusive; M is a metal atom; y is the total number of metal atoms and is from 1 to 4 inclusive; S is a sulfur atom; z is the number of sulfur atoms, and is from 1 to 12 inclusive; u represents the charge of the metallasulfur derivative and may be from −6 to +6 inclusive; v is the number of metallasulfur derivative units in an oligomeric or polymeric structure; I is an ionic atom or group and may be cationic or anionic; and w is the number of cationic or anionic atoms or groups, as required to provide charge neutrality.
 3. The method of claim 1, wherein the stoichiometric ratio of the oxidizing agent to the metallasulfur derivative is less than one equivalent of the oxidizing agent present for every two M-S bonds in the metallasulfur derivative.
 4. The method of claim 1, wherein X and X′ are one or more of chlorine and bromine.
 5. The method of claim 1, wherein X and X′ are chlorine.
 6. The method of claim 1, wherein X and X′ are bromine.
 7. The method of claim 1, wherein X and X′ comprise one or more of a cyanide, a thiocyanide, a sulfate, a thiosulfate, a sulfonate, or a thiosulfonate.
 8. The method of claim 1, further comprising a step of reacting elemental sulfur with a sulfur templating agent to form the metallasulfur derivative prior to the step of reacting the metallasulfur derivative with the oxidizing agent.
 9. The method of claim 8, wherein the reacting the elemental sulfur with a sulfur templating agent to form the metallasulfur derivative is carried out in the presence of water.
 10. The method of claim 1, further comprising a step of isolating the cyclododecasulfur from the cyclododecasulfur-containing reaction mixture.
 11. The method of claim 10, wherein the step of isolating the cyclododecasulfur from the cyclododecasulfur-containing reaction mixture comprises one or more steps chosen from dissolving, heat treating, drying, acid treating, solvent washing, crystallizing, and sedimentation.
 12. The method of claim 10, wherein the step of isolating the cyclododecasulfur comprises treating the cyclododecasulfur with a solvent for the cyclododecasulfur to form a dissolution liquor.
 13. The method of claim 10, further comprising removing metal and metal-containing compounds from the cyclododecasulfur by sedimentation of the metal and the metal-containing compounds.
 14. The method of claim 1, further comprising isolating cyclododecasulfur by heating a cyclododecasulfur-containing mixture in the presence of a solvent to decompose and dissolve in the solvent impurities that are present.
 15. The method of claim 1, further comprising isolating cyclododecasulfur by treating a cyclododecasulfur-containing mixture with an acid to remove any metal or metal-containing compounds that are present.
 16. The method of claim 12, further comprising crystallizing cyclododecasulfur from the dissolution liquor.
 17. A method for the manufacture of cyclododecasulfur, the method comprising: (i) reacting cyclooctasulfur, tetramethylethylenediamine, and zinc to form a tetramethylethylenediamine/Zn(S₆) complex; and (ii) reacting the complex with an oxidizing agent, wherein the oxidizing agent is characterized by the formula: X—X′ wherein X and X′ are the same or different and are selected from the group consisting of halogens or pseudohalogens.
 18. The method of claim 17, wherein the step of reacting the cyclooctasulfur, the tetramethylethylenediamine, and the zinc to form a tetramethylethylene-diamine/Zn(S₆) complex is carried out in the presence of water. 